This is a python program that measures how connected subreddit communities are to each other.

The metric used is to take the proportion of comments made in each subreddit, by each commenter in the target subreddit, and then weigh the results proportionally to how active they are in the target subreddit.

#An overview of the metric and algorithm

dictionary findConnectedSubreddits (subreddit sub)
    for all commenters usr of sub
        let usr.prop be the proportion of comments in sub made by usr

        let usr.totalComments = 0
        for all subreddits usrSub that usr commented in
            let usr.dist[commSub] be the number of comments made by usr in usrSub
            usr.totalComments += usr.dist[commSub]

        for all subreddits usrSub that usr commented in
            sub.connection[usrSub] += usr.dist[usrSub] * usr.prop

    return sub.connection

#Installation and usage

You will need to have python 2.7.8 installed, as well as pip. In Ubuntu/Debian:

sudo apt-get install python
sudo apt-get install python-pip python-dev build-essential 

This program also requires you install PRAW, a library used to access the Reddit API in Python

sudo pip install praw

As well as a few more scientific computing Python packages..

sudo apt-get install python-scipy python-matplotlib python-tk python-sklearn

And to use the program, just open up get_data.py, and set the x_subs python list to your desired subreddits (yeah this is gross sorry). And then:

python get_data.py

This gathers all the data from reddit (this may take a while). To analyze the data and output the dendrograms:

python analyze_data.py

And voila!

#Example outputs

There's also a second way to use the program, if you just do:

python project.py YourSubredditHere 

If you want to analyze more than 10 commenters and 10 of their comments each, then add an integer argument

python project.py YourSubredditHere 100

This will result in 100 of the previous comments being analyzed, and 100 of each commenter’s other comments being analyzed for a total of 100 x 100 = 10000 comments (assuming no repeat commenters). Careful though, time / requests increases proportional to the square of this number. 100 will take a minute or two, 500 - 45 minutes or so. 1000 - go put a pot of coffee on.

project.py will output a textfile in the folder with the most frequent subreddits commented in at the top, with percentages on the right.

You can also compare two communities, or one community against reddit as a whole, by using 3 arguments:

python project.py AskReddit all 300

This will give a contrast between AskReddit commenters and general reddit commenters (/r/all is the combination of all subreddits). Or you can contrast two specific communities:

python project.py javascript python 400

This will output a text file with a list of communities and a number beside it, such as JavaScript 10001.4394 Java 1.24 Ruby 0.54

The way to interpret these results is that Javascript commenters are 10001.4394 times as likely to post in /r/JavaScript as Python commenters are. JavaScript commenters are 24% more likely to post in Java than Python commenters are, but that Javascript commenters are only 54% as likely to post in /r/Ruby as python commenters are.