Networks Demystified 7: Doing Co-Citation Analyses

So this is awkward. I’ve published Networks Demystified 7: Doing Citation Analyses before Networks Demystified 6: Organizing Your Twitter Lists. What depraved lunatic would do such a thing? The kind of depraved lunatic that is teaching this very subject twice in the next two weeks: deal with it, you’ll get your twitterstructions soon, internet. In the meantime, enjoy the irregular nature of the scottbot irregular.

And this is part 7 of my increasingly inaccurately named trilogy of instructional network analysis posts (1 network basics, 2 degree, 3 power laws, 4 co-citation analysis, 5 communities and PageRank, 6 this space left intentionally blank). I’m covering how to actually do citation analyses, so it’s a continuation of part 4 of the series. If you want to know what citation analysis is and why to do it, as well as a laundry list of previous examples in the humanities and social sciences, go read that post. If you want to just finally be able to analyze citations, like you’ve always dreamed, read on. 1

You’re going to need two things for these instructions: The Sci2 Tool, and either a subscription to the multi-gazillion dollar ISI Web of Science database, or this sample dataset. The Sci2 (Science of Science) Tool is a fairly buggy program (I’m allowed to say that because I’m kinda off-and-on the development team and I wrote half the user manual) that specializes in ingesting data of various formats and turning them into networks for analysis and visualization. It’s a good tool to use before you run to Gephi to make your networks pretty, and has a growing list of available plugins. If you already have the Sci2 Tool, download it again, because there’s a new version and it doesn’t auto-update. Go download it. It’s 80mb, I’ll wait.

Once you’ve registered for (not my decision, don’t blame me!) and downloaded the tool, extract the zip folder wherever you want, no install necessary. The first thing to do is increase the amount of memory available to the program, assuming you have at least a gig of RAM on your computer. We’re going to be doing some intensive analysis, so you’ll need the extra space. Edit sci2.ini; on Windows, that can be done by right-clicking on the file and selecting ‘edit’; on Mac, I dunno, elbow-click and press ‘CHANGO’? I have no idea how things work on Macs. (Sorry Mac-folk! We’ve actually documented in more detail how to increase memory – on both Windows and Mac – here)

Once editing the file, you’ll see a nigh-unintelligble string of letters and numbers that end in “-Xmx350m”. Assuming you have more than a gig of RAM on your computer, change that to “-Xmx1000m”. If you don’t have more RAM, really, you should go get some. Or use only a quarter of the dataset provided. Save it and close the text editor.

Run Sci2.exe We didn’t pay Microsoft to register the app, so if you’re on Windows, you may get a OHMYGODWARNING sign. Click ‘run anyway’ and safely let my team’s software hack your computer and use it to send pictures of cats to famous network scientists. (No, we’ll be good, promise). You’ll get to a screen remarkably like Figure 7. Leave it open, and if you’re at an institution that pays ISI Web of Science the big bucks, head there now. Otherwise ignore this and just download the sample dataset.

Downloading Data

I’m a historian of science, so let’s look for history of science articles. Search for ‘Isis‘ as a ‘Publication Name’ from the drop-down menu (see Figure 1) and notice that, as of 9/23/2013, there are 14,858 results (see Figure 2).

Figure 1: Searching for Isis as the name of a publication.
Figure 1: Searching for Isis as the name of a publication.
Figure 2: Isis periodical search results.
Figure 2: Isis periodical search results.

This is a list of every publication in the journal ISIS. Each individual record includes bibliographic material, abstract, and the list of references that are cited in the article. To get a reasonable dataset to work with, we’re going to download every article ever published in ISIS, of which there are 1,189. The rest of the records are book reviews, notes, etc. Select only the articles by clicking the checkbox next to ‘articles’ on the left side of the results screen and clicking ‘refine’.

The next step is to download all the records. This web service limits you to 500 records per download, so you’re going to need to download 3 separate files (records 1-500, 501-1000, and 1001-1189) and combine them together, which is a fairly complicated step, so pay close attention. There’s a little “Send to:” drop-down menu at the top of the search results (Figure 3). Click it, and click ‘Other File Formats’.

Figure 3: Saving Web of Science records.
Figure 3: Saving Web of Science records.

At the pop-up box, check the radio box for records 1 to 500 and enter those numbers, change the record content to ‘Full Record and Cited References’, and change the file format to ‘Plain Text’ (Figure 4). Save the file somewhere you’ll be able to find it. Do this twice more, changing the numbers to 501-1000 and 1001-1189, saving these files as well.

Figure 4: Parameters for downloading Web of Science files.
Figure 4: Parameters for downloading Web of Science files.

You’ll end up with three files, possibly named: savedrecs.txt, savedrecs(1).txt, and savedrecs(2).txt. If you open one up (Figure 5), you’ll see that each individual article gets its own several-dozen lines, and includes information like author, title, keywords, abstract, and (importantly in our case) cited references.

Figure 5: An example Isis record.
Figure 5: An example ISIS record.
Figure 6: The end of an ISIS record file.
Figure 6: The end of an ISIS record file.

You’ll also notice (Figures 5 & 6) that first two lines and last line of every file are special header and footer lines. If we want to merge the three files so that the Sci2 Tool can understand it, we have to delete the footer of the first file, the header and footer of the second file, and the header of the last file, so that the new text file only has one header at the beginning, one footer at the end, and none in between. Those of you who are familiar enough with a text editor (and let’s be honest, it should be everyone reading this) go ahead and copy the three files into one huge file with only one header and footer. If you’re feeling lazy, just download it here.

Creating a Citation Network

Now open the Sci2 Tool (Figure 7) and go to File->Load in the drop-down menu. Find your super file with all of ISIS and open it, loading it as an ‘ISI flat format’ file (Figure 8).

Figure 7: The Sci2 Tool.
Figure 7: The Sci2 Tool.
Figure 8: Loading a file as an ISI flat format file.
Figure 8: Loading a file as an ISI flat format file.

If all goes correctly, two new files should appear in the Data Manager, the pane on the right-hand side of the software. I’ll take a bit of a detour here to explain the Sci2 Tool.

The main ‘Console’ pane on the top-left will include a complete log of your workflow, including all the various algorithms you use, what settings and parameters you use with them, and how to cite the various ones you use. When you close the program, a copy of the text in the ‘Console’ pain will save itself as a log file in the program directory so you can go back to it later and see what exactly you did.

The ‘Scheduler’ pane on the bottom is just that: it shows you what algorithms are currently running and what already ran. You can safely ignore it.

Along with the drop-down menus at the top, the already-mentioned ‘Data Manager’ pane on the right is where you’ll be spending most of your time. Every time you load a file, it will appear in the data manager. Every time you run an algorithm on or manipulate that file in some way, a copy of it with the new changes will appear hierarchically nested below the original file. This is so, if you make a mistake, want to use an earlier version of the file, or want to run run a different set of analyses, you can still do so. You can right-click on files in the data manager to view or save them in various file formats. It is important to remember to make sure that the appropriate file is selected in the data manager when you run an analysis, as it’s easy to accidentally run an algorithm on some other random data file.

With that in mind, once your file is loaded, make sure to select (by left-clicking) the ‘1189 Unique ISI Records’ data file in the data manager. If you right-click and view the file, it should open up in Excel (Figure 9) or whatever your default *.csv viewer is, and you’ll see that the previous text file has been converted to a spreadsheet. You can look through it to see what the data look like.

Figure 9: All of the ISIS History of Science journal articles as a csv.
Figure 9: All of the ISIS History of Science journal articles as a csv.

When you’re done ogling at all the pretty data, close the spreadsheet and go back to the tool. Making sure the ‘1189 Unique ISI Records’ file is selected, go to ‘Data Preparation -> Extract Paper Citation Network’ in the drop-down menu.

Voilà! You now have a history of science citation network. The algorithm spits out two files: ‘Extracted paper-citation network’, which is the network file itself, and ‘Paper information’, which is a spreadsheet that includes all the nodes in the network (in this case, articles that either were published in ISIS or are cited by them). It includes a ‘localCitationCount’ column, which tells you how frequently a work is cited within the dataset (Shapin’s Leviathan and the Air Pump‘ is cited 16 times, you’ll see if you open up the file), and a ‘globalCitationCount’ column, which is how many times ISI Web of Science thinks the article has been cited overall, not just within the dataset (Merton’s ” The Matthew effect in science II” is cited 183 times overall). ‘globalCitationCount’ statistics are of course only available for the records you downloaded, so you have them for ISIS published articles, but none of the other records.

Select ‘Extracted paper-citation network’ in the data manager. From the drop-down menu, run ‘Analysis -> Networks -> Network Analysis Toolkit (NAT)’. It’s a good idea to run this on any network you have, just to see the basic statistics of what you’re working with. The details will appear in the console window (Figure 10).

Figure 10: Network analysis toolkit output on the ISIS citation network.
Figure 10: Network analysis toolkit output on the ISIS citation network.

There are a few things worth noting right away. The first is that there are 52,479 nodes; that means that our adorable little dataset of 1,189 articles actually referenced over 50,000 other works between them, about 50 refs/article. The second fact worth noting is that there are 54,915 directed edges, which is the total number of direct citations in the dataset. One directed edge is a citation from a citing node (an ISIS article) to a cited node (either an ISIS article, or a book, or whatever the author decides to reference).

The last bit worth pointing out is the number of weakly connected components, and the size of the largest connected component. Each weakly connected component is a chunk of the network connected by citation chains: if article A and B are the only articles which cite article C, if article C cites nothing else, and if A and B are uncited by any other articles, they together make a weakly connected component. As soon as another citation link comes from or to them, it becomes part of that component. In our case, the biggest component is 46,971 nodes, which means that most of the nodes in the network are connected to each other. That’s important, it means history of science as represented by ISIS is relatively cohesive. There are 215 weakly connected components in all, small islands that are disconnected from the mainland.

If you have Gephi installed, you can visualize the network by selecting ‘Extracted paper-citation network’ in the data manager and clicking ‘Visualization -> Networks -> Gephi’, though what you do from there is beyond the scope of these instructions. It also probably won’t make a heck of a lot of sense: there aren’t many situations where visualizing a citation network are actually useful. It’s what’s called a Directed Acyclic Graph, which are generally the most visually boring graphs around (don’t cite me on this).

I do have a very important warning. You can tell it’s important because it’s bold. The Sci2 Tool was made by my advisor Katy Börner as a tool for people with similar research to her own, whose interests lie in modeling and predicting the spread of information on a network. As such, the direction of citation edges created by the tool are opposite what many expect. They go from the cited source to the citing source, because the idea is that’s the direction that information flows, rather than from the citing source to the cited source. As a historian, I’m more interested in considering the network in the reverse direction: citing to cited, as that gives more agency to the author. More details in the footnote. 2

Great, now that that’s out of the way, let’s get to the more interesting analyses. Select ‘Extracted paper-citation network’ in the data manager and run ‘Data Preparation -> Extract Document Co-Citation Network’. And then wait. Have you waited for a while? Good, wait some more. This is a process. And 50,000 articles is a lot of articles. While you’re waiting, re-read Networks Demystified 4: Co-Citation Analysis to get an idea of what it is you’re doing and why you want to do it.

Okay, we’re done (assuming you increased the allotted memory to the tool like we discussed earlier). You’re no presented the ‘Co-citation Similarity Network’ in the data manager, and you should, once again, run ‘Analysis -> Networks -> Network Analysis Toolkit (NAT)’ in the Data Manager. This as well will take some time, and you’ll see why shortly.

Figure 11: Network analysis toolkit of the ISIS co-citation network.
Figure 11: Network analysis toolkit of the ISIS co-citation network.

Notice that while there are the same number of nodes (citing or cited articles) as before, 52,479, the number of edges went from 54,915 to 2,160,275, a 40x increase. Why? Because every time two articles are cited together, they get an edge between them and, according to the ‘Average degree’ in the console pane, each article or book is cited alongside an average of 82 other works.

In order to make the analysis and visualization of this network easier we’re going to significantly cut its size. Recall that document co-citation networks connect documents that are cited alongside each other, and that the weight of that connection is increased the more often the two documents appear together in a bibliography. What we’re going to do here is drastically reduce the network’s size deleting any edge between documents unless they’ve been cited together more than once. Select ‘Co-citation Similarity Network’ and run ‘Preprocessing -> Networks -> Extract Edges Above or Below Value’. Use the default settings (Figure 12).

Note that when you’re doing a scholarly citation analysis, cutting all the edges below a certain value (called ‘thresholding’) is usually a bad idea unless you know exactly how it will affect your study. We’re doing it here to make the walkthrough easier.

Figure 12: Extracting edges to reduce the size of the network.
Figure 12: Extracting edges to reduce the size of the network.

Run ‘Analysis -> Networks -> Network Analysis Toolkit (NAT)’ on the new ‘Edges above 1 by weight’ dataset, and note that the network has been reduced from two million edges to three thousand edges, a much more manageable number for our purposes. You’ll also see that there are 51,313 isolated nodes: nodes that are no longer connected to the network because we cut so many edges in our mindless rampage. Who cares about them? Let’s delete them too! Select ‘Edges above 1 by weight’ and run ‘Preprocessing -> Networks -> Delete Isolates’, and watch as fifty thousand precious history of science citations vanish in a puff of metadata. Gone.

If you run the Network Analysis Toolkit on the new network, you’ll see that we’re left with a small co-citation net of 1,166 documents and 3,344 co-citations between them. The average degree tells us that each document is connected to, on average, 6 other documents, and that the largest connected component contains 476 documents.

So now’s the moment of truth, the time to visualize all your hard work. If you know how to use Gephi, and have it installed, select ‘With isolates removed’ in the data manager and run ‘Visualization -> Networks -> Gephi’. If you don’t, run ‘Visualization -> Networks -> GUESS’ instead, and give it a minute to load. You will be presented with this stunning work of art vaguely reminiscent of last night’s spaghetti and meatball dinner (Figure 13).

Figure 13: GUESS in all its glory.
Figure 13: GUESS in all its glory.

Fear not! The first step to prettifying the network is to run ‘Layout -> GEM’ and then ‘Layout -> Bin Pack’. Better already, right? Then you can make edits using the graph modifier below (or using python commands in the interpreter), but the friendly folks at my lab have put together a script for you that will do that automatically. Run ‘Script -> Run Script’.

When you do, you will be presented with a godawful java applet that automatically sticks you in some horrible temp directory that you have to find your way out of. In the ‘Look In:’ navigation drop-down, find your way back to your desktop or your documents directory and then find wherever you installed the Sci2 Tool. In the Sci2 directory, there’s a folder called ‘scripts’, and in the ‘scripts’ folder, there’s a ‘GUESS’ folder, and in the ‘GUESS’ folder you will find the holy grail. Select ‘’ and press ‘open’.

Magic! Your document co-citation network is now all green and pretty, and you can zoom in and out using either the +/- button on the left, or using your mouse wheel and clicking and dragging on the network itself. It’ll look a bit like Figure 14.

Figure 14: Co-Citation network in GUESS.
Figure 14: Co-Citation network in GUESS.

If you feel more dangerous and cool, you can try visualizing the same network in Gephi, and it might come out something like Figure 15.

Figure 15: Gephi's document co-citation network, with nodes sized by how frequently they're cited in ISIS.
Figure 15: Gephi’s document co-citation network, with nodes sized by how frequently they’re cited in ISIS. Click to enlarge.

That’s it! You’ve co-cited a dataset. I hope you feel proud of yourself, because you should. And all without breaking a sweat. If you want (and you should want), you can save your results by right clicking the various files in the data manager you want to save. I’d recommend saving the most recent file, ‘With isolates removed’, and saving it as an NWB file, which is fairly easy to read and is the Sci2 Tool’s native format.

Stay-tuned for the paradoxically earlier-numbered Networks Demystified 6, on organizing your twitter feed.


  1. Part 4 also links to a few great tutorials on how to do this with programming, but if you don’t know the first thing about programming, start here instead.
  2. Those of you who know network basics, keep this in mind when running your analyses: PageRank, In & Out Degree, etc., may be opposite of what you expect, with the papers that cite the most sources as those with the highest In-Degree and PageRank. If this is opposite your workflow, you can fairly easily change the data by hand in a spreadsheet editor or with regular expressions.

From Trees to Webs: Uprooting Knowledge through Visualization

[update: here are some of the pretty pictures I will be showing off in The Hague]

The blog’s been quiet lately; my attention has been occupied by various journal submissions and a new book in the works, but I figured my readers would be interested in one of those forthcoming publications. This is an article [preprint] I’m presenting at the Universal Decimal Classification Seminar in The Hague this October, on the history of how we’ve illustrated the interconnections of knowledge and scholarly domains. It’s basically two stories: one of how we shifted from understanding the world hierarchically to understanding it as a flat web of interconnected parts, and the other of how the thing itself and knowledge of that thing became separated.

Porphyrian Tree: tree of Aristotle's categories from the 6th century. [via]
Porphyrian Tree: tree of Aristotle’s categories originally dating from the 6th century. [via some random website about trees]
A few caveats worth noting: first, because I didn’t want to deal with the copyright issues, there are no actual illustrations in the paper. For the presentation, I’m going to compile a powerpoint with all the necessary attributions and post it alongside this paper so you can all see the relevant pretty pictures. For your viewing pleasure, though, I’ve included some of the illustrations in this blog post.

An interpretation of the classification of knowledge from Hobbes' Leviathan. [via e-ducation]
An interpretation of the classification of knowledge from Hobbes’ Leviathan. [via e-ducation]
Second, because the this is a presentation directed at information scientists, the paper is organized linearly and with a sense of inevitability; or, as my fellow historians would say, it’s very whiggish. I regret not having the space to explore the nuances of the historical narrative, but it would distract from the point and context of this presentation. I plan on writing a more thorough article to submit to a history journal at a later date, hopefully fitting more squarely in the historiographic rhetorical tradition.

H.G. Wells' idea of how students should be taught. [via H.G. Wells, 1938. World Brain. Doubleday, Doran & Co., Inc]
H.G. Wells’ idea of how students should be taught. [via H.G. Wells, 1938. World Brain. Doubleday, Doran & Co., Inc]
In the meantime, if you’re interested in reading the pre-print draft, here it is! All comments are welcome, as like I said, I’d like to make this into a fuller scholarly article beyond the published conference proceedings. I was excited to put this up now, but I’ll probably have a new version with full citation information within the week, if you’re looking to enter this into Zotero/Mendeley/etc. Also, hey! I think this is the first post on the Irregular that has absolutely nothing to do with data analysis.

Recent map of science by Kevin Boyack, Dick Klavans, W. Bradford Paley, and Katy Börner. [via SEED magazine]
Recent map of science by Kevin Boyack, Dick Klavans, W. Bradford Paley, and Katy Börner. [via SEED magazine]

Networks Demystified 4: Co-Citation Analysis

This installment of Networks Demystified is the first one that’s actually applied. A few days ago, a discussion arose over twitter involving citation networks, and this post fills the dual purpose of continuing that discussion, and teaching a bit about basic citation analysis. If you’re looking for the very basics of networks, see part 1 and part 2. Part 3 is a warning for anyone who feels the urge to say “power law.” To recap: nodes are the dots/points in the network, edges are the lines/arrows/connections.

Understanding Sociology, Philosophy, and Literary Theory using One Easy Method™!

The growing availability of humanities and social science (HSS) citation data in databases like ISI’s Web of Science (warning: GIANT paywall. Good luck getting access if your university doesn’t subscribe.) has led to a groundswell of recent blog activity in the area, mostly by the humanists and social scientists themselves. Which is a good thing, because citation analyses of HSS will happen whether we’re involving in doing them or not, so if humanists start becoming familiar with the methods, at least we can begin getting humanistically informed citation analyses of our own data.

ISI Web of Science paywall
The size of ISI’s Web of Science paywall. You shall not pass. [via]
This is a sort of weird post. It’s about history and philosophy of science, by way of social history, by way of literary theory, by way of philosophy, by way of sociology. About this time last year, Dan Wang asked the question Is There a Canon in Economic Sociology (pdf)? Wang was searching for a set of core texts for economic sociology, using a set of 52 syllabi regarding the subject. It’s a reasonable first pass at the question, counting how often each article appears in the syllabi (plus some more complex measurements) as well as how often individual authors appear. Those numbers are used to support the hypothesis that there is a strongly present canon, both of authors and individual articles, in economic sociology. This is an example of an extremely simple bimodal network analysis where there are two varieties of node: syllabi or articles. Each syllabi cites multiple articles, and several of those articles are cited by multiple syllabi. The top part of Figure 1 is what this would look like in a basic network representation.

Figure 1: basic bimodal network (top) and the resulting co-citation network (bottom). [Via Mark Newman, PNAS]
Figure 1: basic bimodal network (top) and the resulting co-citation network (bottom). [via Mark Newman]
Wang was also curious how instructors felt these articles fit together, so he used a common method called co-citation analysis to answer the question. The idea is that if two articles are cited in the same syllabus, they are probably related, so they get an edge drawn between them. He further restricted his analysis so that articles had to appear together in the same class session, rather than the the same syllabus, to be considered related to each other. What results is a new network (Figure 1, below) of article similarity based on how frequently they appear together (how frequently they are cited by the same source). In Figure 1, you can see that because article H and article F are both cited in syllabus class session 3, they get an edge drawn between them.

A further restriction was then placed on the network, what’s called a threshold. Two articles would only get an edge drawn between them if they were cited by at least 2 different class sessions (threshold = 2). The resulting economic sociology syllabus co-citation network looked like Figure 2, pulled from the original article. From this picture, one can begin to develop a clear sense of the demarcations of subjects and areas within economic sociology, thus splitting the canon into its constituent parts.

Figure 2: Co-citation network in economic sociology. [via]
Figure 2: Co-citation network in economic sociology. Edge thickness represents how often articles appear together in syllabi, and node size is based on a measure of centrality. [via]
In short order, Kieran Healy blogged a reply to this study, providing his own interpretations of the graph and what the various clusters represented. Remember Healy’s name, as it’s important later in the story. Two days after Healy’s blog post, Neal Caren took inspiration and created a co-citation analysis of sociology more broadly–not just economic sociology–using data he downloaded from ISI’s Web of Science (remember the giant paywall from before?). Instead of using syllabi, Caren looked at articles found in American Journal of Sociology, American Sociological Review, Social Forces and Social Problems since 2008. Web of Science gave him a list of every citation from every article in those journals, and he performed the same sort of co-citation analysis as Dan Wang did with syllabi, but at a much larger scale.

Because the dataset Caren used was so much larger, he had to enforce much stricter thresholds to keep the visualization manageable. Whereas Wang’s graph showed all articles, and connected them if they appeared together in more than 2 class sessions, Caren’s graph only connected articles which were cited together more than 4 times (threshold = 4). Further, a cited article wouldn’t even appear on the network visualization unless the article itself had been cited 8 or more times, thus reducing the amount of articles appearing on the visualization overall. The final network had 397 nodes (articles) and 1,597 edges (connections between articles). He also used a popular community detection algorithm to color the different article nodes based on which other articles they were most related to. Figure 3 shows the resulting network, and clicking on it will lead to an interactive version.

Figure 3: Neal Caren's sociology co-citation analysis. Click the picture to see the interactive version. [via]
Figure 3: Neal Caren’s sociology co-citation analysis. Click the picture to see the interactive version. [via]
Caren adds a bit of contextual description in his blog post, explaining what the various clusters represent and why this visualization is a valid and useful one for the field of sociology. Notably, at the end of the post, he shares his raw data, a python script for analyzing it, and all the code for visualizing the network and making it interactive and pretty.

Jump forward a year. Kieran Healy, the one who wrote the original post inspiring Neal Caren’s, decides to try his own hand at a citation analysis using some of the code and methods that Neal Caren had posted about. Healy’s blog post, created just a few days ago, looks at the field of philosophy through the now familiar co-citation analysis. Healy’s analysis covers 20 years of four major philosophy journals, consisting of 2,200 articles. These articles together make over 34,000 citations, although many of the cited articles are duplicates of articles that had already been cited. Healy writes:

The more often any single paper is cited, the more important it’s likely to be. But the more often any two papers are cited together, the more likely they are to be part of some research question or ongoing problem or conversation topic within the discipline.

With a dataset this large, the resulting co-citation network wound up having over a million edges, or connections between co-cited articles. Healy decides to only focus on the 500 most highly-cited items in the journals (not the best practice for a co-citation analysis, but I’ll address that in a later post), resulting in only articles that had been cited more than 10 times within the four journal dataset to be present in the network. Figure 4 shows the resulting network, which like Figure 3, can be clicked on to reach the interactive version.

Figure 4: Kieran Healy's co-citation analysis of four philosophy journals. Click for interactivity. [via]
Figure 4: Kieran Healy’s co-citation analysis of four philosophy journals. Click for interactivity. [via]
The post goes on to provide a fairly thorough and interesting analysis of the various communities formed by article clusters, thus giving a description of the general philosophy landscape as it currently stands. The next day, Healy posted a follow-up delving further into citations of philosopher David Lewis, and citation frequencies by gender. Going through the most highly cited 500 or so philosophy articles by hand, Healy finds that 3.6% of the articles are written by women; 6.3% are written by David Lewis; the overwhelming majority are written by white men. It’s not lost on me that the overwhelming majority of people doing these citation analyses are also white men – someone please help change that? Healy posted a second follow-up a few days later, worth reading, on his reasoning behind which journals he used and why he looked at citations in general. He concludes “The 1990s were not the 1950s. And yet essentially none of the women from this cohort are cited in the conversation with anything close to the same frequency, despite working in comparable areas, publishing in comparable venues, and even in many cases having jobs at comparable departments.”

Merely short days after Healy’s articles, Jonathan Goodwin became inspired, using the same code Healy and Caren used to perform a co-citation analysis of Literary Theory Journals. He began by concluding that these co-citation analysis were much more useful (better) than his previous attempts at direct citation analysis. About four decades of bibliometric research backs up Goodwin’s claim. Figure 5 shows Goodwin’s Literary Theory co-citation network, drawn from five journals and clickable for the interactive version, where he adds a bit of code so that the user can determine herself what threshold she wants to cut off co-citation weights. Goodwin describes the code to create the effect on his github account. In a follow-up post, directly inspired by Healy’s, Goodwin looks at citations to women in literary theory. His results? When a feminist theory journal is included, 8 of the top 30 authors are women (27%); when that journal is not included, only 2 of the top 30 authors are women (7%).

Figure 5: Goodwin's literary theory co-citation network. [via]
Figure 5: Goodwin’s literary theory co-citation network. [via]

At the Speed of Blog

Just after these blog posts were published, a quick twitter exchange between Jonathan Goodwin, John Theibault, and myself (part of it readable here) spurred Goodwin, in the space of 20 minutes, to download, prepare, and visualize the co-citation data of four social history journals over 40 years. He used ISI Web of Science data, Neal Caren’s code, a bit of his own, and a few other bits of open script which he generously cites and links to. All of this is to highlight not only the phenomenal speed of research when unencumbered by the traditional research process, but also the ease with which these sorts of analysis can be accomplished. Most of this is done using some (fairly simple) programming, but there are just as easy solutions if you don’t know how to or don’t care to code–one specifically which I’ll mention later, the Sci2 Tool. From data to visualization can take a matter of minutes; a first pass at interpretation won’t take much longer. These are fast analyses, pretty useful for getting a general overview of some discipline, and can provide quite a bit of material for deeper analysis.

The social history dataset is now sitting on Goodwin’s blog just waiting to be interpreted by the right expert. If you or anyone you know is familiar with social history, take a stab at figuring out what the analysis reveals, and then let us all know in a blog post of your own. I’ll be posting a little more about it as well soon, though I’m no expert of the discipline. Also, if you’re interested in citation analysis in the humanities, and you’ll be at DH2013 in Nebraska, I’ll be chairing a session all about citations in the humanities featuring an impressive lineup of scholars. Come join us and bring questions, July 17th at 10:30am.

Discovering History and Philosophy of Science

Before I wrap up, it’s worth mentioning that in one of Kieran Healy’s blog posts, he thanks Brad Wray for pointing out some corrections in the dataset. Brad Wray is one of the few people to have published a recent philosophy citation analysis in a philosophy journal. Wray is a top-notch philosopher, but his citation analysis (Philosophy of Science: What are the Key Journals in the Field?, Erkenntnis, May 2010 72:3, paywalled) falls a bit short of the mark, and as this is an instructional piece on co-citation analysis, it’s worth taking some time here to explore why.

Wray’s article’s thesis is that “there is little evidence that there is such a field as the history and philosophy of science (HPS). Rather, philosophy of science is most properly conceived of as a sub-field of philosophy.” He arrives at this conclusion via a citation analysis of three well-respected monographs, A Companion to the Philosophy of ScienceThe Routledge Companion to Philosophy of Science, and The Philosophy of Science edited by David Papineau, in total comprising 149 articles. Wray then counts how many times major journals are cited within each article, and shows that in most cases, the most frequently cited journals across the board are strict philosophy of science journals.

The data used to support Wray’s thesis–that there is no such field as history & philosophy of science (HPS)–is this coarse-level journal citation data. No history of science journal is listed in the top 10-15 journals cited by the three monographs, and HPS journals appear, but very infrequently. Of the evidence, Wray writes “if there were such a field as history and philosophy of science, one would expect scholars in that field to be citing publications in the leading history of science journal. But, it appears that philosophy of science is largely independent of the history of science.”

It is curious that Wray would suggest that total citations from strict philosophy of science companions can be used as evidence of whether a related but distinct field, HPS, actually exists. Low citations from philosophy of science to history of science is that evidence. Instead, a more nuanced approach to this problem would be similar to the approach above: co-citation analysis. Perhaps HPS can be found by analyzing citations from journals which are ostensibly HPS, rather than analyzing three focused philosophy of science monographs. If a cluster of articles should appear in a co-citation analysis, this would be strong evidence that such a discipline currently exists among citing articles. If such a cluster does not appear, this would not be evidence of the non-existence of HPS (absence of evidence ≠ evidence of absence), but that the dataset or the analysis type is not suited to finding whatever HPS might be. A more thorough analysis would be required to actually disprove the existence of HPS, although one imagines it would be difficult explaining that disproof to the people who think that’s what they are.

With this in mind, I decided to perform the same sort of co-citation analysis as Dan Wang, Kieran Healy, Neal Caren, and Jonathan Goodwin, and see what could be found. I drew from 15 journals classified in ISI’s Web of Science as “History & Philosophy of Science” (British Journal for the Philosophy of Science, Journal of Philosophy, Synthese, Philosophy of Science, Studies in History and Philosophy of Science, Annals of Science, Archive for History of Exact Sciences, British Journal for the History of Science, Historical Studies in the Natural Sciences, History and Philosophy of the Life Sciences, History of Science, Isis, Journal for the History of Astronomoy, Osiris, Social Studies of Science, Studies in History and Philosophy of Modern Physics, and Technology and Culture). In all I collected 12,510 articles dating from 1956, with over 300,000 citations between them. For the purpose of not wanting to overheat my laptop, I decided to restrict my analysis to looking only at those articles within the dataset; that is, if any article from any of the 15 journals cited any other article from one of the 15 journals, it was included in the analysis.

I also changed my unit of analysis from the article to the author. I didn’t want to see how often two articles were cited by some third article–I wanted to see how often two authors were cited together within some article. The resulting co-citation analysis gives author-author pairs rather than article-article pairs, like the examples above. In all, there were 7,449 authors in the dataset, and 10,775 connections between author pairs; I did not threshold edges, so the some authors in the network were cited together only once, and some as many as 60 times. To perform the analysis I used the Science of Science (Sci2) Tool, no programming required, (full advertisement disclosure: I’m on the development team), and some co-authors and I have written up how to do a similar analysis in the documentation tutorials.

The resulting author co-citation network, in Figure 6, reveals two fairly distinct clusters of authors. You can click the image to enlarge, but I’ve zoomed in on the two communities, one primarily history of science, the other primarily philosophy of science. At first glance, Wray’s hypothesis appears to be corroborated by the visualization; there’s not much in the way of a central cluster between the two. That said, a closer look at the middle, Figure 7, highlights a group of people whom either have considered themselves within HPS, or others have considered HPS.

Figure 6: Author co-citation network of 15 history & philosophy of science journals. Two authors are connected if they are cited together in some article, and connected more strongly if they are cited together frequently. Click to enlarge. [via me!]
Figure 6: Author co-citation network of 15 history & philosophy of science journals. Two authors are connected if they are cited together in some article, and connected more strongly if they are cited together frequently. Click to enlarge. [via me!] 
Figure 7: Author co-citation analysis of history and philosophy of science journals, zoomed in on the area between history and philosophy, with authors highlighted who might be considered HPS. Click to enlarge.
Figure 7: Author co-citation analysis of history and philosophy of science journals, zoomed in on the area between history and philosophy, with authors highlighted who might be considered HPS. Click to enlarge.

Figures 6 & 7 don’t prove anything, but they do suggest that within citation patterns, history of science and philosophy of science are clearly more cohesive than some combined HPS might be. Figure 7 suggests there might be more to the story, and what is needed in the next step to try to pin down HPS–if indeed it exists as some sort of cohesive unit–is to find articles that specifically self-identify as HPS, and through their citation and language patterns, try to see what they have in common with and what separates them from the larger community. A more thorough set of analytics, visualizations, and tables, which I’ll explain further at some point, can be found here (apologies for the pdf, this was originally made in preparation for another project).

The reason I bring up this example is not to disparage Wray, whose work did a good job of finding the key journals in philosophy of science, but to argue that we as humanists need to make sure the methods we borrow match the questions we ask. Co-citation analysis happens to be a pretty good method for exploring the question Wray asked in his thesis, but there are many more situations where it wouldn’t be particularly useful. The recent influx of blog posts on the subject, and the upcoming DH2013 session, is exciting, because it means humanists are beginning to take citation analysis seriously and are exploring the various situations in which its methods are appropriate. I look forward to seeing what comes out of the Social History data analysis, as well as future directions this research will take.

Acceptances to Digital Humanities 2013 (part 1)

The 2013 Digital Humanities conference in Nebraska just released its program with a list of papers and participants. As some readers may recall, when the initial round of reviews went out for the conference, I tried my hand at analyzing submissions to DH2013. Now that the schedule has been released, the data available puts us in a unique position to compare proposed against accepted submissions, thus potentially revealing how what research is being done compares with what research the DH community (through reviews) finds good or interesting. In my last post, I showed that literary studies and data/text mining submissions were at the top of the list; only half as many studies were historical rather than literary. Archive work and visualizations were also near the top of the list, above multimedia, web, and content analyses, though each of those were high as well.

A keyword analysis showed that while Visualization wasn’t necessarily at the top of the list, it was the most central concept connecting the rest of the conference together. Nobody knows (and few care) what DH really means; however, these analyses present the factors that bind together those who call themselves digital humanists and submit to its main conference. The post below explores to what extent submissions and acceptances align. I preserve anonymity wherever possible, as submitting authors did not do so with the expectation that turned down submission data would be public.

It’s worth starting out with a few basic acceptance summary statistics. As I don’t have access to poster data yet, nor do I have access to withdrawals, I can’t calculate the full acceptance rate, but there are a few numbers worth mentioning. Just take all of the percentages as a lower bounds, where withdrawals or posters might make the acceptance rate higher. Of the 144 long papers submitted, 66.6% of them (96) were accepted, although only 57.6% (83) were accepted as long papers; another 13 were accepted as short papers instead. Half of the submitted panels were accepted, although curiously, one of the panels was accepted instead as a long paper. For short papers, only 55.9% of those submitted were accepted. There were 66 poster submissions, but I do not know how many of those were accepted, or how many other submissions were accepted as posters instead. In all, excluding posters, 60.9% of submitted proposals were accepted. More long papers than short papers were submitted, but roughly equal numbers of both were accepted. People who were turned down should feel comforted by the fact that they faced some stiff competition.

As with most quantitative analyses, the interesting bits come more when comparing internal data than when looking at everything in aggregate. The first three graphs do just that, and are in fact the same data, but ordered differently. When authors submitted their papers to the conference, they could pick any number of keywords from a controlled vocabulary. Looking at how many times each keyword was submitted with a paper (Figure 1) can give us a basic sense of what people are doing in the digital humanities. From Figure 1 we see (again, as a version of this viz appeared in the last post) that “Literary Studies” and “Text Mining” are the most popular keywords among those who submitted to DH2013; the rest you can see for yourself. The total height of the bar (red + yellow) represents the number of total submissions to the conference.

Acceptance rates of DH2013 by Keywords attached to submissions, sorted by number of submissions.
Figure 1: Acceptance rates of DH2013 by Keywords attached to submissions, sorted by number of submissions. (click to enlarge)

Figure 2 shows the same data as Figure 1, but sorted by acceptance rates rather than the total number of submissions. As before, because we don’t know about poster acceptance rates or withdrawals, you should take these data with a grain of salt, but assuming a fairly uniform withdrawal/poster rate, we can still make some basic observations. It’s also worth pointing out that the fewer overall submissions to the conference with a certain keyword, the less statistically meaningful the acceptance rate; with only one submission, whether or not it’s accepted could as much be due to chance as due to some trend in the minds of DH reviewers.

With those caveats in mind, Figure 2 can be explored. One thing that immediately pops out is that “Literary Studies” and “Text Mining” both have higher than average acceptance rates, suggesting that not only are a lot of DHers doing that kind of research; that kind of research is still interesting enough that a large portion of it is getting accepted, as well. Contrast this with the topic of “Visualization,” whose acceptance rate is closer to 40%, significantly fewer than the average acceptance rate of 60%. Perhaps this means that most reviewers thought visualizations worked better as posters, the data for which we do not have, or perhaps it means that the relatively low barrier to entry on visualizations and their ensuing proliferation make them more fun to do than interesting to read or review.

“Digitisation – Theory and Practice” has a nearly 60% acceptance rate, yet “Digitisation; Resource Creation; and Discovery” has around 40%, suggesting that perhaps reviewers are more interested in discussions about digitisation than the actual projects themselves, even though far more “Digitisation; Resource Creation; and Discovery” papers were submitted than “”Digitisation – Theory and Practice.” The imbalance between what was submitted and what was accepted on that front is particularly telling, and worth a more in-depth exploration by those who are closer to the subject. Also tucked at the bottom of the acceptance rate list are three related keywords “Digital Humanities – Institutional Support, “Digital Humanities – Facilities,” & “Glam: Galleries; Libraries; Archives; Museums,” each with a 25% acceptance rate. It’s clear the reviewers were not nearly as interested in digital humanities infrastructure as they were in digital humanities research. As I’ve noted a few times before, “Historical Studies” is also not well-represented, with both a lower acceptance rate than average and a lower submission rate than average. Modern digital humanities, at least as it is represented by this conference, appears far more literary than historical.

Figure 2. Acceptance rates of DH2013 by Keywords attached to submissions, sorted by number of accepted papers.
Figure 2. Acceptance rates of DH2013 by Keywords attached to submissions, sorted by number of accepted papers. (click to enlarge)

Figure 3, once again, has the same data as Figures 2 and 1, but is this time sorted simply by accepted papers and panels. This is the front face of DH2013; the landscape of the conference (and by proxy the discipline) as seen by those attending. While this reorientation of the graph doesn’t show us much we haven’t already seen, it does emphasize the oddly low acceptance rates of infrastructural submissions (facilities, libraries, museums, institutions, etc.) While visualization acceptance rates were a bit low, attendees of the conference will still see a great number of them, because the initial submission rate was so high. Conference goers will see that DH maintains a heavy focus on the many aspects of text: its analysis, its preservation, its interfaces, and so forth. The web also appears well-represented, both in the study of it and development on it. Metadata is perhaps not as strong a focus as it once was (historical DH conference analysis would help in confirming this speculation on my part), and reflexivity, while high (nearly 20 “Digital Humanities – Nature and Significance” submissions), is far from overwhelming.

A few dozen papers will be presented on multimedia beyond simple text – a small but not insignificant subgroup. Fewer still are papers on maps, stylometry, or medieval studies, three subgroups I imagine once had greater representation. They currently each show about the same force as gender studies, which had a surprisingly high acceptance rate of 85% and is likely up-and-coming in the DH world. Pedagogy was much better represented in submissions than acceptances, and a newcomer to the field coming to the conference for the first time would be forgiven in thinking pedagogy was less of an important subject in DH than veterans might think it is.

Figure 3. Acceptance rates of DH2013 by Keywords attached to submissions, sorted by acceptance rate. (click to enlarge)
Figure 3. Acceptance rates of DH2013 by Keywords attached to submissions, sorted by acceptance rate. (click to enlarge)

As what’s written so far is already a giant wall of text, I’ll go ahead and leave it at this for now. When next I have some time I’ll start analyzing some networks of keywords and titles to find which keywords tend to be used together, and whatever other interesting things might pop up. Suggestions and requests, as always, are welcome.



Nobody has said so to my face, but sometimes I’m scared that some of my readers secretly think I’m single-handedly assisting in the downfall of academia as we know it. You see, I was the associate instructor of an information visualization MOOC this past semester, and next Spring I’ll be putting together my own MOOC on information visualization for the digital humanities. It’s an odd position to be in, when much of the anti-DH rhetoric is against MOOCs while so few DHers actually support them (and it seems most vehemently denounce them). I’ve occasionally wondered if I’m the mostly-fictional strawman the anti-DH crowd is actually railing against. I don’t think I am, and I think it’s well-past time I posted my rationale of why.

This post itself was prompted by two others; one by Adam Crymble asking if The Programming Historian is a MOOC, and the other by Jonathan Rees on why even if you say your MOOC is going to be different, it probably won’t be. That last post was referenced by Andrew Goldstone:

With that in mind, let me preface by saying I’m a well-meaning MOOCer, and I think that if you match good intentions with reasonable actions, MOOCs can actually be used for good. How you build, deploy, and use a MOOC can go a long way, and it seems a lot of the fear behind them assumes there is one and only one inevitable path for them to go down which would ultimately result in the loss of academic jobs and a decrease in education standards.

Let’s begin with the oft-quoted Cathy Davidson, “If we can be replaced replaced by a computer screen, we should be.” I don’t believe Davidson is advocating for what Rees accuses her of in the above blog post. One prevailing argument against MOOCs is that the professors are distant, the interactivity is minimal-to-non-existent, and the overall student experience is one of weak detachment. I wonder, though, how many thousand-large undergraduate lectures offer better experiences; many do, I’m sure, but many also do not. In those cases, it seems a more engaging lecturer, at least, might be warranted. I doubt many-if-any MOOC teachers believe there are any other situations which could warrant the replacement of a university course with a MOOC beyond those where the student experience is already so abysmal that anything might help.

The question then arises, in those few situations where MOOCs might be better for enrolled students, what havoc might they wreak on already worsening faculty job opportunities? The toll on teaching in the face of automation might match the toll of the skilled craftsmen in the face of the industrial and eventually mechanical revolution. If you feel angry at replacing laborers with machines in situations where the latter are just (or nearly) as good as the former, and at a fraction of the cost, then you’ll likely also believe MOOCs replacing giant undergrad lectures (which, let’s face it, are often closer to unskilled than to skilled labor in this metaphor) is also unethical.

Rees echoes this fear of automation on the student’s end, suggesting “forcing students into MOOCs as a last resort is like automating your wedding or the birth of your first child.  You’re taking something that ought to depend upon the glorious unpredictability of human interaction and turning it into mass-produced, impersonal, disposable schlock.” The fear is echoed as well by Adam Crymble in his Programming Historian piece, when he says “what sets a MOOC apart from a classroom-based course is a belief that the tutor-tutee relationship can be depersonalized and made redundant. MOOCs replace this relationship with a series of steps. If you learn the steps in the right order and engage actively with the material you learn what you need to know and who needs teacher?”

MOOCs can happen to you! via cogdogblog.
MOOCs can happen to you! via cogdogblog.

The problem is that this entire dialogue rests on assumptions of Crymble and others taking the form that those who support MOOCs do so because, deep down, they believe “If you learn the steps in the right order and engage actively with the material you learn what you need to know and who needs teacher?” It is this set of assumptions that I would like to push against; the idea that all MOOCs must inevitably lead to automated teaching, regardless of the intentions, and that they exist as classroom replacements. I argue that, if designed and utilized correctly, MOOCs can lead to classroom augmentations and in fact can be designed in a way that they can no more be used to replace classrooms than massively-distributed textbooks can.

When Katy Börner and our team designed and built the Information Visualization MOOC, we did so using Google’s open source Course Builder, with the intention of opening knowledge to whomever wanted to learn it regardless of whether they could afford to enroll in one of the few universities around that offers this sort of course. Each of the lectures were recordings of usual lectures for that class, but cut up into more bite-sized chunks, and included tutorials on how to use software. We ran the MOOC concurrently with our graduate course of the same focus, and we used the MOOC as a sort of video textbook that (I hope) was more concise and engaging than most information visualization textbooks out there, and (importantly) completely free to the students. Students watched pre-recorded lectures at home  and then we discussed the lessons and did hands-on training during class time, not dissimilar from the style of flipped teaching.

For those not enrolled in the physical course, we opened up the lectures to anyone who wanted to join in, and created a series of tests and assignments which required students to work together in small teams of 4-5 on real world client data if they wanted to get credit for the course. Many just wanted to learn, and didn’t care about credit. Some still took the exams because they wanted to know how well they’d learned the data, even if they weren’t taking the course credit. Some just did the client projects, because they thought it would give them good real-world experience, but didn’t take the tests and go for the credit. The “credit,” by the way, was a badge from Mozilla Open Badges, and we designed them to be particularly difficult to achieve because we wanted them to mean something. We also hand-graded the client projects.

The IVMOOC Badge.
The IVMOOC Badge.

The thing is, at no time did we ever equate the MOOC with a graduate course, or ever suggest that it could be taken as a replacement credit  instead of some real course. And, by building the course in Google’s course-builder and hosting it ourselves, we have complete control over it; universities can’t take it and change it around as they see fit to offer it for credit. I suppose it’s possible that some university out there might allow students to wave a methodology credit if they get our badge, but I fail to see how that would be any different from universities offering course-waving for students reading a textbook on their own and taking some standard test afterward; it’s done, but not often.

In short, we offer the MOOC as a free and open textbook, not as a classroom replacement. Within the classroom, we use it as a tool for augmenting instruction. For those who choose to do assignments, and perform well on them with their student teams, we acknowledge their good work with a badge rather than a university credit. The fear that MOOCs will necessarily automate teachers away is no more well-founded than the idea that textbooks-and-standardized-tests would; further, if administrators choose to use MOOCs for this purpose, they are no more justified in doing this than they would be justified in replacing teachers with textbooks. That they still might is of course a frightening prospect, and something we need to guard against, but should no more be blamed on MOOC instructors than they would be blamed on textbook authors in the alternative scenario. It doesn’t seem we’re any different from what Adam Crymble described The Programming Historian to be (recall: definitely not a MOOC).

We’re making it easier for people to teach themselves interesting and useful things. Whether administrators use that for good or ill is a separate issue. Whether more open and free training trumps our need to employ all the wandering academics out there is a separate issue – as is whether or not that dichotomy is even a valid one. As it stands now, though, I’m proud of the work we’ve done on the IVMOOC, I’m proud of the students of the physical course, and I’m especially proud of all the amazing students around the world who came out of the MOOC producing beautiful visualization projects, and are better prepared for life in a data-rich world.

Liveblogged Review of Macroanalysis by Matthew L. Jockers, Part 2

I just got Matthew L. Jocker’s Macroanalysis in the mail, and I’m excited enough about it to liveblog my review. Here’s the review of part II (Analysis), chapter 5 (metadata). Read Part 1, Part 3, …

Part II: Analysis

Part II of Macroanalysis moves from framing the discussion to presenting a series of case studies around a theme, starting fairly simply in claims and types of analyses and moving into the complex. This section takes up 130 of the 200 pages; in a discipline (or whatever DH is) which has coasted too long on claims that the proof of its utility will be in the pudding (eventually), it’s refreshing to see a book that is at least 65% pudding. That said, with so much substance – particularly with so much new substance – Jockers opens his arguments up for specific critiques.

Aiming for more pudding-based scholarly capital in DH. via brenthor.
Aiming for more pudding-based scholarly capital in DH. via brenthor.

Quantitative arguments must by their nature be particularly explicit, without the circuitous language humanists might use to sidestep critiques. Elijah Meeks and others have been arguing for some time now that the requirement to solidify an argument in such a way will ultimately be a benefit to the humanities, allowing faster iteration and improvement on theories. In that spirit, for this section, I offer my critiques of Jockers’ mathematical arguments not because I think they are poor quality, but because I think they are particularly good, and further fine-tuning can only improve them. The review will now proceed one chapter at a time.


Jockers begins his analysis exploring what he calls the “lowest hanging fruit of literary history.” Low hanging fruit can be pretty amazing, as Ted Underwood says, and Jockers wields some fairly simple data in impressive ways. The aim of this chapter is to show that powerful insights can be achieved using long-existing collections of library metadata, using a collection of nearly 800 Irish American works over 250 years as a sample dataset for analysis. Jockers introduces and offsets his results against the work of Charles Fanning, whom he describes as the expert in Irish American fiction in aggregate. A pre-DH scholar, Fanning was limited to looking through only the books he had time to read; an impressive many, according to Jockers, but perhaps not enough. He profiles 300 works, fewer than half of those represented in Jockers’ database.

The first claim made in this chapter is one that argues against a primary assumption of Fanning’s. Fanning expends considerable effort explaining why there was a dearth of Irish American literature between 1900-1930; Jockers’ data show this dearth barely existed. Instead, the data suggest, it was only eastern Irish men who had stopped writing. The vacuum did not exist west of the Mississippi, among men or women. Five charts are shown as evidence, one of books published over time, and the other four breaking publication down by gender and location.

Jockers is careful many times to make the point that, with so few data, the results are suggestive rather than conclusive. This, to my mind, is too understated. For the majority of dates in question, the database holds fewer than 6 books per year. When breaking down by gender and location, that number is twice cut in half. Though the explanations of the effects in the graphs are plausible, the likelihood of noise outweighing signal at this granularity is a bit too high to be able to distinguish a just-so story from a credible explanation. Had the data been aggregated in five- or ten-year intervals (as they are in a later figure 5.6), rather than simply averaged across them, the results may have been more credible. The argument may be brought up that, when aggregating across larger intervals, the question of where to break up the data becomes important; however, cutting the data into yearly chunks from January to December is no more arbitrary than cutting them into decades.

There are at least two confounding factors one needs to take into account when doing a temporal analysis like this. The first is that what actually happened in history may be causally contingent, which is to say, there’s no particularly useful causal explanation or historical narrative for a trend. It’s just accidental; the right authors were in the right place at the right time, and all happened to publish books in the same year. Generally speaking, if only around five books are published a year, though sometimes that number is zero and sometimes than number is ten, any trends that we see (say, five years with only a book or two) may credibly be considered due to chance alone, rather than some underlying effect of gender or culture bias.

The second confound is the representativeness of the data sample to some underlying ground truth. Datasets are not necessarily representative of anything, however as defined by Jockers, his dataset ought to be representative of all Irish American literature within a 250 year timespan. That’s his gold standard. The dataset obviously does not represent all books published under this criteria, so the question is how well do his publication numbers match up with the actual numbers he’s interested in. Jockers is in a bit of luck here, because what he’s interested in is whether or not there was a resounding silence among Irish authors; thus, no matter what number his charts show, if they’re more than one or two, it’s enough to disprove Fanning’s hypothesized silence. Any dearth in his data may be accidental; any large publications numbers are not.

This example chart compares a potential "real" underlying publication rate against several simulated potential sample datasets Jockers might have, created by multiplying the "real" dataset by some random number between 0 and 1.
This example chart compares a potential “real” underlying publication rate against several simulated potential sample datasets Jockers might have, created by multiplying the “real” dataset by some random number between 0 and 1.

I created the above graphic to better explain the second confounding factor of problematic samples. The thick black line, we can pretend, is the actual number of books published by Irish American authors between 1900 and 1925. As mentioned, Jockers would only know about a subset of those books, so each of the four dotted lines represents a possible dataset that he could be looking at in his database instead of the real, underlying data. I created these four different dotted lines by just multiplying the underlying real data by a random number between 0 and 1 1. From this chart it should be clear that it would not be possible for him to report an influx of books when there was a dearth (for example, in 1910, no potential sample dataset would show more than two books published). However, if Jockers wanted to make any other claims besides whether or not there was a dearth (as he tentatively does later on), his available data may be entirely misleading. For example, looking at the red line, Run 4, would suggest that ever-more books were being published between 1910 and 1918, when in fact that number should have decreased rapidly after about 1912.

The correction included in Macroanalysis for this potential difficulty was to use 5-year moving averages for the numbers rather than just showing the raw counts. I would suggest that, because the actual numbers are so small and a change of a small handful of books would look like a huge shift on the graph, this method of aggregation is insufficient to represent the uncertainty of the data. Though his charts show moving averages, they still shows small changes year-by-year, which creates a false sense of precision. Jockers’ chart 5.6, which aggregates by decade and does not show these little changes, does a much better job reflecting the uncertainty. Had the data showed hundreds of books per year, the earlier visualizations would have been more justifiable, as small changes would have amounted to less emphasized shifts in the graph.

It’s worth spending extra time on choices of visual representation, because we have not collectively arrived at a good visual language for humanities data, uncertain as they often are. Nor do we have a set of standard practices in place, as quantitative scientists often do, to represent our data. That lack of standard practice is clear in Macroanalysis; the graphs all have subtitles but no titles, which makes immediate reading difficult. Similarly, axis labels (“count” or “5-year average”) are unclear, and should more accurately reflect the data (“books published per year”), putting the aggregation-level in either an axis subtitle or the legend. Some graphs have no axis labels at all (e.g., 5.12-5.17). Their meanings are clear enough to those who read the text, or those familiar with ngram-style analyses, but should be more clear at-a-glance.

Questions of visual representation and certainty aside, Jockers still provides several powerful observations and insights in this chapter. Figure 5.6, which shows Irish American fiction per capita, reveals that westerners published at a much higher relative rate than easterners, which is a trend worth explaining (and Jockers does) that would not have been visible without this sort of quantitative analysis. The chapter goes on to list many other credible assessments and claims in light of the available data, as well as a litany of potential further questions that might be explored with this sort of analysis.  He also makes the important point that, without quantitative analysis, “cherry-picking of evidence in support of a broad hypothesis seems inevitable in the close-reading scholarly traditions.” Jockers does not go so far as to point out the extension of that rule in data analysis; with so many visible correlations in a quantitative study, one could also cherry-pick those which support one’s hypothesis. That said, cherry-picking no longer seems inevitable. Jockers makes the point that Fanning’s dearth thesis was false because his study was anecdotal, an issue Jockers’ dataset did not suffer from. Quantitative evidence, he claims, is not in competition with evidence from close reading; both together will result in a “more accurate picture of our subject.”

The second half of the chapter moves from publication counting to word analysis. Jockers shows, for example, that eastern authors are less likely to use words in book titles that identify their work as ‘Irish’ than western authors, suggesting lower prejudicial pressures west of the Mississippi may be the cause. He then complexifies the analysis further, looking at “lexical diversity” across titles in any given year – that is, a year is more lexically diverse if the titles of books published that year are more unique and dissimilar from one another. Fanning suggests the years of the famine were marked by a lack of imagination in Irish literature; Jockers’ data supports this claim by showing those years had a lower lexical diversity among book titles. Without getting too much into the math, as this review of a single chapter has already gone on too long, it’s worth pointing out that both the number of titles and the average length of titles in a given year can affect the lexical diversity metric. Jockers points this out in a footnote, but there should have been a graph comparing number of titles per year, length per year, and lexical diversity, to let the readers decide whether the first two variables accounted for the third, or whether to trust the graph as evidence for Fanning’s lack-of-imagination thesis.

One of the particularly fantastic qualities about this sort of research is that readers can follow along at home, exploring on their own if they get some idea from what was brought up in the text. For example, Jockers shows that the word ‘century’ in British novel titles is popular leading up to and shortly after the turn of the nineteenth century. Oddly, in the larger corpus of literature (and it seems English language books in general), we can use to see that, rather than losing steam around 1830, use of ‘century’ in most novel titles actually increases until about 1860, before dipping briefly. Moving past titles (and fiction in general) to full text search, google ngrams shows us a small dip around 1810 followed by continued growth of the word ‘century’ in the full text of published books. These different patterns are interesting particularly because they suggest there was something unique about the British novelists’ use of the word ‘century’ that is worth explaining. Oppose this with Jockers’ chart of the word ‘castle’ in British book titles, whose trends actually correspond quite well to the bookworm trend until the end of the chart, around 1830. [edit: Ben Schmidt points out in the comments that bookworm searches full text, not just metadata as I assumed, so this comparison is much less credible.]

Use of the word 'castle' in the metadata of books provided by Compare with figure 5.14. via bookworm.
Use of the word ‘castle’ in the metadata of books provided by Compare with figure 5.14. via bookworm.

Jockers closes the chapter suggesting that factors including gender, geography, and time help determine what authors write about. That this idea is trivial makes it no less powerful within the context of this book: the chapter is framed by the hypothesis that certain factors influence Irish American literature, and then uses quantitative, empirical evidence to support those claims. It was oddly satisfying reading such a straight-forward approach in the humanities. It’s possible, I suppose, to quibble over whether geography determines what’s written about or whether the sort of person who would write about certain things is also the sort of person more likely to go west, but there can be little doubt over the causal direction of the influence of gender. The idea also fits well with the current complex systems approach to understanding the world, which mathematically suggests that environmental and situational constraints (like gender and location) will steer the unfolding of events in one direction or another. It is not a reductionist environmental determinism so much as a set of probabilities, where certain environments or situations make certain outcomes more likely.

Stay tuned for Part the Third!


  1. If this were a more serious study, I’d have multiplied by a more credible pseudo-random value keeping the dataset a bit closer to the source, but this example works fine for explanatory value

Analyzing submissions to Digital Humanities 2013

Digital Humanities 2013 is on its way; submissions are closed, peers will be reviewing them shortly, and (most importantly for this post) the people behind the conference are experimenting with a new method of matching submissions to reviewers. It’s a bidding process; reviewers take a look at the many submissions and state their reviewing preferences or, when necessary, conflicts of interest. It’s unclear the extent to which these preferences will be accommodated, as this is an experiment on their part. Bethany Nowviskie describes it here. As a potential reviewer, I just went through the process of listing my preferences, and managed to do some data scraping while I was there. How could I not? All 348 submission titles were available to me, as well as their authors, topic selections, and keywords, and given that my submission for this year is all about quantitatively analyzing DH, it was an opportunity I could not pass up. Given that these data are sensitive, and those who submitted did so under the assumption that rejected submissions would remain private, I’m opting not to release the data or any non-aggregated information. I’m also doing my best not to actually read the data in the interest of the privacy of my peers; I suppose you’ll all just have to trust me on that one, though.

So what are people submitting? According to the topics authors assigned to their 348 submissions, 65 submitted articles related to “literary studies,” trailed closely by 64 submissions which pertained to “data mining/ text mining.” Work on archives and visualizations are also up near the top, and only about half as many authors submitted historical studies (37) as those who submitted literary ones (65). This confirms my long suspicion that our current wave of DH (that is, what’s trending and exciting) focuses quite a bit more on literature than history. This makes me sad.  You can see the breakdown in Figure 1 below, and further analysis can be found after.

Figure 1: Number of documents with each topic authors assigned to submissions for DH2013 (click to enlarge).

The majority of authors attached fewer than five topics to their submissions; a small handful included over 15.  Figure 2 shows the number of topics assigned to each document.

Figure 2: The number of topics attached to each document, in order of rank.

I was curious how strongly each topic coupled with other topics, and how topics tended to cluster together in general, so I extracted a topic co-occurrence network. That is, whenever two topics appear on the same document, they are connected by an edge (see Networks Demystified Pt. 1 for a brief introduction to this sort of network); the more times two topics co-occur, the stronger the weight of the edge between them.

Topping off the list at 34 co-occurrences were “Data Mining/ Text Mining” and “Text Analysis,” not terrifically surprising as the the latter generally requires the former, followed by “Data Mining/ Text Mining” and “Content Analysis” at 23 co-occurrences, “Literary Studies” and “Text Analysis” at 22 co-occurrences, “Content Analysis” and “Text Analysis” at 20 co-occurrences, and “Data Mining/ Text Mining” and “Literary Studies” at 19 co-occurrences. Basically what I’m saying here is that Literary Studies, Mining, and Analysis seem to go hand-in-hand.

Knowing my readers, about half of you are already angry with me counting co-occurrences, and rightly so. That measurement is heavily biased by the sheer total number of times a topic is used; if “literary studies” is attached to 65 submissions, it’s much more likely that it will co-occur with any particular topic than topics (like “teaching and pedagogy”) which simply appear more infrequently. The highest frequency topics will co-occur with one another simply by an accident of magnitude.

To account for this, I measured the neighborhood overlap of each node on the topic network. This involves first finding the number of other topics  a pair of two topics shares. For example, “teaching and pedagogy” and “digital humanities – pedagogy and curriculum” each co-occur with several other of the same topics, including “programming,” “interdisciplinary collaboration,” and “project design, organization, management.” I summed up the number topical co-occurrences between each pair of topics, and then divided that total by the number of co-occurrences each node in the pair had individually. In short, I looked at which pairs of topics tended to share similar other topics, making sure to take into account that some topics which are used very frequently might need some normalization. There are better normalization algorithms out there, but I opt to use this one for its simplicity for pedagogical reasons. The method does a great job leveling the playing field between pairs of infrequently-used topics compared to pairs of frequently-used topics, but doesn’t fair so well when looking at a pair where one topic is popular and the other is not. The algorithm is well-described in Figure 3, where the darker the edge, the higher the neighborhood overlap.

Figure 3: The neighborhood overlap between two nodes is how many neighbors (or connections) that pair of nodes shares. As such, A and B share very few connections, so their overlap is low, whereas D and E have quite a high overlap. Via Jaroslav Kuchar.

Neighborhood overlap paints a slightly different picture of the network. The pair of topics with the largest overlap was “Internet / World Wide Web” and “Visualization,” with 90% of their neighbors overlapping. Unsurprisingly, the next-strongest pair was “Teaching and Pedagogy” and “Digital Humanities – Pedagogy and Curriculum.” The data might be used to suggest multiple topics that might be merged into one, and this pair seems to be a pretty good candidate. “Visualization” also closely overlaps “Data Mining/ Text Mining”, which itself (as we saw before) overlaps with “Cultural Studies” and “Literary Studies.” What we see from this close clustering both in overlap and in connection strength is the traces of a fairly coherent subfield out of DH, that of quantitative literary studies. We see a similarly tight-knit cluster between topics concerning archives, databases, analysis, the web, visualizations, and interface design, which suggests another genre in the DH community: the (relatively) recent boom of user interfaces as workbenches for humanists exploring their archives. Figure 4 represents the pairs of topics which overlap to the highest degree; topics without high degrees of pair correspondence don’t appear on the network graph.

Figure 4: Network of topical neighborhood overlap. Edges between topics are weighted according to how structurally similar the two topics are. Topics that are structurally isolated are not represented in this network visualization.

The topics authors chose for each submission were from a controlled vocabulary. Authors also had the opportunity to attach their own keywords to submissions, which unsurprisingly yielded a much more diverse (and often redundant) network of co-occurrences. The resulting network revealed a few surprises: for example, “topic modeling” appears to be much more closely coupled with “visualization” than with “text analysis” or “text mining.” Of course some pairs are not terribly surprising, as with the close connection between “Interdisciplinary” and “Collaboration.” The graph also shows that the organizers have done a pretty good job putting the curated topic list together, as a significant chunk of the high thresholding keywords are also available in the topic list, with a few notable exceptions. “Scholarly Communication,” for example, is a frequently used keyword but not available as a topic – perhaps next year, this sort of analysis can be used to help augment the curated topic list. The keyword network appears in Figure 5. I’ve opted not to include a truly high resolution image to dissuade readers from trying to infer individual documents from the keyword associations.

Figure 5: Which keywords are used together on documents submitted to DH2013? Nodes are colored by cluster, and edges are weighted by number of co-occurrences. Click to enlarge.

There’s quite a bit of rich data here to be explored, and anyone who does have access to the bidding can easily see that the entire point of my group’s submission is exploring the landscape of DH, so there’s definitely more to come on the subject from this blog. I especially look forward to seeing what decisions wind up being made in the peer review process, and whether or how that skews the scholarly landscape at the conference.

On a more reflexive note, looking at the data makes it pretty clear that DH isn’t as fractured as some occasionally suggest (New Media vs. Archives vs. Analysis, etc.). Every document is related to a few others, and they are all of them together connected in a rich family, a network, of Digital Humanities. There are no islands or isolates. While there might be no “The” Digital Humanities, no unifying factor connecting all research, there are Wittgensteinian family resemblances  connecting all of these submissions together, in a cohesive enough whole to suggest that yes, we can reasonably continue to call our confederation a single community. Certainly, there are many sub-communities, but there still exists an internal cohesiveness that allows us to differentiate ourselves from, say, geology or philosophy of mind, which themselves have their own internal cohesiveness.

Making pretty things with R and ggplot2

This isn’t going to be a long tutorial. I’ve just had three people asking how I made the pretty graphs on my last post about counting citations, and I’m almost ashamed to admit how easy it was. Somebody with no experience coding can (I hope) follow these steps and make themselves a pretty picture with the data provided, and understand how it was created.

qplot(Cited, data = sci, geom="density", fill=YearRange, log="x", xlab="Number of Citations", ylab="Density", main="Density of citations per 8 years", alpha=I(.5))

That’s the whole program. Oh, also this table, saved as a csv:

[table id=3 /]


And that was everything I used to produce this graph:

Density graph made with R.

Quick Walkthrough


The first thing you need to make this yourself is the programming language R (an awesome language for statistical analysis) installed on your machine, which you can get here. Download it and install it; it’s okay, Ill wait. Now, R by itself is not fun to code in, so my favorite program to use when writing R code is called RStudio, so go install that too. Now you’re going to have to install the visualization package, which is called ggplot2. You do this from within RStudio itself, so open up the newly installed program. If you’re running Windows Vista or 7, don’t open it up the usual way; right click on the icon and click ‘Run as administrator’ – you need to do this so it’ll actually let you install the package. Once you’ve opened up RStudio, at the bottom of the program there’s a section of your screen labeled ‘Console’, with a blinking text cursor. In the console, type install.packages(“ggplot2”) and hit enter. Congratulations, ggplot2 is now installed.

Now download this R file (‘Save as’) that I showed you before and open it in RStudio (‘File -> Open File’). It should look a lot like that code at the beginning of the post. Now go ahead and download the csv shown above as well, and be sure to put it in the same directory 1 you put the R code. Once you’ve done that, in RStudio click ‘Tools -> Set Working Directory -> To Source File Location’), which will help R figure out where the csv is that you just downloaded.

Before I go on explaining what each line of the code does, run it and see what happens! Near the top of your code on the right side, there should be a list of buttons, on the left one that says ‘Run’ and on the right one that says ‘Source’. Click the button that says ‘Source‘. Voila, a pretty picture!


Now to go through the code itself, we’ll start with line 1. library(ggplot2) just means that that we’re going to be using ggplot2 to make the visualization, and lets R know to look for it when it’s about to put out the graphics.

Line 2 is fairly short as well, sci=read.csv(“scicites.csv”), and it creates a new variable called sci which contains the entire csv file you downloaded earlier. read.csv(“scicites.csv”) is a command that tells R to read the csv file in the parentheses, and setting the variable sci as equal to that read file just saves it.

Line 3 is where the magic happens.

qplot(Cited, data = sci, geom="density", fill=YearRange, log="x", xlab="Number of Citations", ylab="Density", main="Density of citations per 8 years", alpha=I(.5))

The entire line is surrounded by the parenthetical command qplot() which is just our way of telling R “hey, plot this bit in here!” The first thing inside the parentheses is Cited, which you might recall was one of the columns in the CSV file. This is telling qplot() what column of data it’s going to be plotting, in this case, the number of citations that papers have received. Then, we tell qplot() where that data is coming from with the command data = sci, which sets what table the data column is coming from. After that geom=”density” appears. geom is short for ‘Geometric Object’ and it sets what the graph will look like. In this case we’re making a density graph, so we give it “density”, but we could just as easily have used something like “histogram” or “line”.

The next bit is fill=YearRange, which you might recall was another column in the csv. This is a way of breaking the data we’re using into categories; in this case, the data are categorized by which year range they fall into. fill is one way of categorizing the data by filling in the density blobs with automatically assigned colors; another way would be to replace fill with color. Try it and see what happens. After the next comma is log=”x”, which puts the x-axis on a log scale, making the graph a bit easier to read. Take a look at what the graph looks like if you delete that part of it.

Now we have a big chunk of code devoted to labels. xlab=”Number of Citations”, ylab=”Density”, main=”Density of citations per 8 years”. As can probably be surmised, xlab corresponds to the label on the x-axis, ylab corresponds to the label on the y-axis, and main corresponds to the title of the graph. The very last part, before the closing parentheses, is alpha=I(.5)alpha sets the transparency of the basic graph elements, which is why the colored density blobs all look a little bit transparent. I set their transparency to .5 so they’d each still be visible behind the others. You can set the value between 0 and 1, with the former being completely transparent and the latter being completely opaque.

There you have it, easy-peasy. Play around with the csv, try adding your own data, and take a look at this chapter from “ggplot2: Elegant Graphics for Data Analysis” to see what other options are available to you.


  1. thanks Andy for the correction!

How many citations does a paper have to get before it’s significantly above baseline impact for the field?

[Note: This blog post was originally hidden because it’s not aimed at my usual audience. I decided to open it up because, hey, I guess it’s okay for all you humanists and data scientists to know that one of the other hats I wear is that of an informetrician. Another reason I kept it hidden is because I’m pretty scared of how people use citation impact ratings to evaluate research for things like funding and tenure, often at the expense of other methods that ought be used when human livelihoods are at stake. So please don’t do that.]

It depends on the field, and field is defined pretty loosely. This post is in response to a twitter conversation between mrgunn, myself, and some others. mrgunn thinks citation data ought to be freely available, and I agree with him, although I believe data is difficult enough to gather and maintain that a service charge for access is fair, if a clever free alternative is lacking. I’d love to make a clever free alternative (CiteSeerX already is getting there), but the best data still comes from expensive sources like ISI’s Web of Science or Scopus.

At any rate, the question is an empirical one, and one that lots of scientometricians have answered in a number of ways. I’m going to perform my own SSA (Super-Stupid Analysis) here, and I won’t bother taking statistical regression models or Bayesian inferences into account, because you can get a pretty good sense of “impact” (if you take citations to be a good proxy for impact, which is debatable – I won’t even get into using citations as a proxy for quality) using some fairly simple statistics. For the mathy and interested, a forthcoming paper by Evans, Hopkins, and Kaube treats the subject more seriously in Universality of Performance Indicators based on Citation and Reference Counts.

I decided to use the field of Scientometrics, because it’s fairly self-contained (and I love being meta), and I drew my data from ISI’s Web of Science. I retrieved all articles published in the journal Scientometrics up until 2009, which is a nicely representative sample of the field, and then counted the number of citations to each article in a given year. Keep in mind that if you’re wondering how much your Scientometrics paper stood out above its peers in citations with this chart, you have to use ISI’s citation count to your paper, otherwise you’re comparing apples to something else that isn’t apples.

Figure 1. Histogram of citations to papers, with the height of each bar representing the number of papers cited x times. The colors break down the bars by year. (Click to enlarge)
Figure 2. Same as Figure 1, but with the x axis on a log scale.

According to Figure 1 and Figure 2 (Fig. 2 is the same as Fig. 1 but with the x axis on a log scale to make the data a bit easier to read), it’s immediately clear that citations aren’t normally distributed. This tells us right away that some basic statistics simply won’t tell us much with regards to this data. For example, if we take the average number of citations per paper, by adding up each paper’s citation count and dividing it by the total number of papers, we get 7.8 citations per paper. However, because the data are so skewed to one side, over 70% of the papers in the set fall below that average (that is, 70% of papers are cited fewer than 7 times). In this case, a slightly better measurement would be the median, which is 4. That is, about half the papers have fewer than four citations. About a fifth of the papers have no citations at all.

If we look at the colors of Figure 1, which breaks down each bar by year, we can see that the data aren’t really evenly distributed by years, either. Figure 3 breaks this down a bit better.

Figure 3. Number of papers to articles in the journal Scientometrics, colored by number of citations each received.

In Figure 3, you can see the amount of papers published in a given year, and the colors represent how many citations each paper got that year, with the red end of the spectrum showing papers cited very little, and the violet end of the spectrum showing highly cited papers. Immediately we see that the most recent papers don’t have many highly cited articles, so the first thing we should do is normalize by year. That is, an article published this year shouldn’t be placed against the same standards as an article that’s had twenty years to slowly accrue citations.

To make these data a bit easier to deal with, I’ve sliced the set into 8-year chunks. There are smarter ways to do this, but like I said, we’re keeping the analysis simple for the sake of presentation. Figure 4 is the same as Figure 3, but separated out into the appropriate time slices.

Figure 4. Same as figure 3, but separated into 8 year time slices.

Now, to get back to the original question, mrgunn asked how many citations a paper needs to be above the fold. Intuitively, we’d probably call a paper highly impactful if it’s in the blue or violet sections of its time slice (sorry for those of you who are colorblind, I just mean the small top-most area). There’s another way to look at these data that’ll make it a bit easier to eyeball how much more citations a paper’s received than its peers; a density graph. Figure 5 shows just that.

Figure 5. Each color blob represents a time slice, with the height at any given point representing the proportion of papers in that chunk of time which have x citations. The x axis is on a log scale.

Looking at Figure 5, it’s easy to see that a paper published before 2008 with fewer than half a dozen citations is clearly below the norm. If the paper were published after 2008, it could be above the norm even if it had only a small handful of citations. A hundred citations is clearly “highly impactful” regardless of the year the paper was published. To get a better sense of papers that are above the baseline, we can take a look at the actual numbers.

The table below (excuse the crappy formatting, I’ve never tried to embed a big table in WP before) shows the percent of papers which have x citations or fewer in a given time slice. That is, 24% of papers published before 1984 have no citations to them, 31% of papers published before 1984 have 0 or 1 citations to them, 40% of papers published before 1984 have 0, 1, or 2 citations to them, and so forth. That means if you published a paper in Scientometrics  in 1999 and ISI’s Web of Science says you’ve received 15 citations, it means your paper has received more citations than 80% of the other papers published between 1992 and 2000.

[table id=2 /]


The conversation also brought up the point of whether this should be a clear binary at the ends of the spectrum (paper A is low impact because it received only a handful of citations, paper B is high impact because it received 150, but we can’t really tell anything in between), or whether we could get a more nuanced few of the spectrum. A combined qualitative/quantitative analysis would be required for a really good answer to that question, but looking at the numbers in the table above, we can see pretty quickly that while 1 citation is pretty different from 2 citations, 38 citations is pretty much the same as 39. That is, the “jitter” of precision probably increases exponentially the more citations you’ve received, such that with very few citations the “impact” precision is quite high, and that precision gets exponentially lower the more citations you’ve received.

All this being said, I do agree with mrgunn that a free and easy to use resource for this sort of analysis would be good. However, because citations often don’t equate to quality, I’d be afraid this tool would just make it easier and more likely for people to make sweeping and inaccurate quality measurements for the purpose of individual evaluations.

Early Modern Letters Online

Early modern history! Science! Letters! Data! Four of my favoritest things have been combined in this brand new beta release of Early Modern Letters Online from Oxford University.



EMLO (what an adorable acronym, I kind of what to tickle it) is Oxford’s answer to a metadata database (metadatabase?) of, you guessed it, early modern letters. This is pretty much a gold standard metadata project. It’s still in beta, so there are some interface kinks and desirable features not-yet-implemented, but it has all the right ingredients for a great project:

  • Information is free and open; I’m even told it will be downloadable at some point.
  • Developed by a combination of historians (via Cultures of Knowledge) and librarians (via the Bodleian Library) working in tandem.
  • The interface is fast, easy, and includes faceted browsing.
  • Has a fantastic interface for adding your own data.
  • Actually includes citation guidelines thank you so much.
  • Visualizations for at-a-glance understanding of data.
  • Links to full transcripts, abstracts, and hard-copies where available.
  • Lots of other fantastic things.

Sorry if I go on about how fantastic this catalog is – like I said, I love letters so much. The index itself includes roughly 12,000 people, 4,000 locations, 60,000 letters, 9,000 images, and 26,000 additional comments. It is without a doubt the largest public letters database currently available. Between the data being compiled by this group, along with that of the CKCC in the Netherlands, the Electronic Enlightenment Project at Oxford, Stanford’s Mapping the Republic of Letters project, and R.A. Hatch‘s research collection, there will without a doubt soon be hundreds of thousands of letters which can be tracked, read, and analyzed with absolute ease. The mind boggles.

Bodleian Card Catalogue Summaries

Without a doubt, the coolest and most unique feature this project brings to the table is the digitization of Bodleian Card Catalogue, a fifty-two drawer index-card cabinet filled with summaries of nearly 50,000 letters held in the library, all compiled by the Bodleian staff many years ago. In lieu of full transcriptions, digitizations, or translations, these summary cards are an amazing resource by themselves. Many of the letters in the EMLO collection include these summaries as full-text abstracts.

One of the Bodleian summaries showing Heinsius looking far and wide for primary sources, much like we’re doing right now…

The collection also includes the correspondences of John Aubrey (1,037 letters), Comenius (526), Hartlib (4,589 many including transcripts), Edward Lhwyd (2,139 many including transcripts), Martin Lister (1,141), John Selden (355), and John Wallis (2,002). The advanced search allows you to look for only letters with full transcripts or abstracts available. As someone who’s worked with a lot of letters catalogs of varying qualities, it is refreshing to see this one being upfront about unknown/uncertain values. It would, however, be nice if they included the editor’s best guess of dates and locations, or perhaps inferred locations/dates from the other information available. (For example, if birth and death dates are known, it is likely a letter was not written by someone before or after those dates.)


In the interest of full disclosure, I should note that, much like with the CKCC letters interface, I spent some time working with the Cultures of Knowledge team on visualizations for EMLO. Their group was absolutely fantastic to work with, with impressive resources and outstanding expertise. The result of the collaboration was the integration of visualizations in metadata summaries, the first of which is a simple bar chart showing the numbers of letters written, received, and mentioned in per year of any given individual in the catalog. Besides being useful for getting an at-a-glance idea of the data, these charts actually proved really useful for data cleaning.

Sir Robert Crane (1604-1643)

In the above screenshot from previous versions of the data, Robert Crane is shown to have been addressed letters in the mid 1650s, several years after his reported death. While these could also have been spotted automatically, there are many instances where a few letters are dated very close to a birth or death date, and they often turn out to miss-reported. Visualizations can be great tools for data cleaning as a form of sanity test. This is the new, corrected version of Robert Crane’s page. They are using d3.js, a fantastic javascript library for building visualizations.

Because I can’t do anything with letters without looking at them as a network, I decided to put together some visualizations using Sci2 and Gephi. In both cases, the Sci2 tool was used for data preparation and analysis, and the final network was visualized in GUESS and Gephi, respectively. The first graph shows network in detail with edges, and names visible for the most “central” correspondents. The second visualization is without edges, with each correspondent clustered according to their place in the overall network, with the most prominent figures in each cluster visible.

Built with Sci2/Guess
Built with Sci2/Gephi

The graphs show us that this is not a fully connected network. There are many islands of one or two letters or a small handful of letters. These can be indicative of a prestige bias in the data. That is, the collection contains many letters from the most prestigious correspondents, and increasingly fewer as the prestige of the correspondent decreases. Put in another way, there are many letters from a few, and few letters from many. This is a characteristic shared with power law and other “long tail” distributions. The jumbled community structure at the center of the second graph is especially interesting, and it would be worth comparing these communities against institutions and informal societies at the time. Knowledge of large-scale patterns in a network can help determine what sort of analyses are best for the data at hand. More on this in particular will be coming in the next few weeks.

It’s also worth pointing out these visualizations as another tool for data-checking. You may notice, on the bottom left-hand corner of the first network visualization, two separate Edward Lhwyds with virtually the same networks of correspondence. This meant there were two distinct entities in their database referring to the same individual – a problem which has since been corrected.

More Letters!

Notice that the EMLO site makes it very clear that they are open to contributions. There are many letters datasets out there, some digitized, some still languishing idly on dead trees, and until they are all combined, we will be limited in the scope of the research possible. We can always use more. If you are in any way responsible for an early-modern letters collection, meta-data or full-text, please help by opening that collection up and making it integrable with the other sets out there. It will do the scholarly world a great service, and get us that much closer to understanding the processes underlying scholarly communication in general. The folks at Oxford are providing a great example, and I look forward to watching this project as it grows and improves.