Full access to the Twitter API in Matlab via R

[Update: This page is no longer relevant. If you are here to interact with Twitter via the API using Matlab, then you want Twitty. The rest is here for posterity.]

Having slowly degraded my ability to interact with proper operating systems and obscure programming languages (e.g. NSFW), I find it difficult to keep up with “modern” ways of programming. So when it comes to doing something that might be conceivably trivial for serious programmers, I tend to struggle.

One example is accessing the complete Twitter API, including those searches that involve being authorised/authenticated via OAuth. So while I had no problem doing search queries and tweeting via a nice Matlab function, I was unable to find a simple way to find the followers/friends of public users and their retweets/replies using the parts of the API that required authentication/authorisation. So once I did, I thought it would be appropriate to pass along my approach so that it would be available to other fervent Matlab users who may wish to do the same.

And since I have long lost the ability to do anything complicated in programming, this will be necessarily be a beginner’s guide to accessing Twitter via MATLAB. I skip over much of the details and specifics but I hope to cover the particular steps that tripped me up along the way.

1. Create an app on Twitter. The most important thing to remember on this step is to leave the callback URL blank. Or delete it afterwards, which is what I did after much too much mucking around trying to work out why I could not access a PIN (more on this later). The other thing you will need to remember is to include Read and Write privileges.

2. If you don’t already have it, download and install R. I’m using version 2.14.0. In my version under Windows, I immediately installed the ROAuth and twitteR packages from within the R application.

3. Run the following commands inside R. Rather than elaborate on these here, it will be better if you peruse the documentation and examples associated with the packages to understand how they work [because I don’t]. Note that I am downloading a cacert file, which will be used later on [I think it is necessary].

  • setwd(“D:\blah\some-directory\\”); [remember to use \ for directories]
  • library(twitteR)
  • library(ROAuth)
  • download.file(url=”http://curl.haxx.se/ca/cacert.pem”, destfile=”cacert.pem”) [make sure it ends up in the right place]
  • KEY <- “********************” [consumer key from your twitter app]
  • SECRET <- “***********************************” [consumer secret from your twitter app]
  • cred <- OAuthFactory$new(consumerKey = KEY,
  •     consumerSecret = SECRET,
  •     requestURL = “https://api.twitter.com/oauth/request_token”,
  •     accessURL = “https://api.twitter.com/oauth/access_token”,
  •     authURL = “https://api.twitter.com/oauth/authorize”)
  • cred$handshake(cainfo=”cacert.pem”)

At this point you will be presented with a statement containing a URL to go and find a PIN from Twitter. If you have set up your application correctly (no callback URL), you can simply navigate to that website and copy and paste your pin number inside.

4. Inside R again, save the OAuth object (cred) to a suitable filename. I have saved mine as Cred.RData. The command is “save”. It’s easy to find.

5. Create a new R script with the following commands:

  • setwd(“D:\blah\some-directory\\”)
  • args <- commandArgs(TRUE)
  • library(twitteR)
  • library(ROAuth)
  • load(‘D:\blah\some-directory\Cred.RData’)
  • cred$isVerified()
  • print(cred$OAuthRequest(args[1], “GET”, ssl.verifypeer = FALSE))

You will notice that this script includes “args[1]”, which we are going to pass from within MATLAB when we call the script. You will also notice that we have loaded the old OAuth object, which means that you will no longer need to enter the PIN each time you want to access the Twitter API.

Those of you who are following carefully will also notice that this is a particularly unsafe way of requesting information from Twitter, and is prone to man-in-the-middle attacks. I can’t imagine how the resulting strings could be dangerous, and there is no private information contained in what is being sent around, so I am comfortable with this until I am convinced otherwise.

6. In MATLAB, simply create the html you will use to call the Twitter API, for example, noting the method for producing the correct quotation marks (without it, the command line will not know how to interpret your ampersands correctly):

htmlx = ‘”https://api.twitter.com/1/statuses/user_timeline.json?include_entities=true&include_rts=true&screen_name=KRuddMP&count=2″’;

In this case, the html request will collect up a certain Australian politician’s last two tweets, which always make for interesting reading.

7. Then, to ask R to run the script you have written. To do this, you need only run the following command from within MATLAB (or within a function in MATLAB, of course):

  • [status,result] = system([‘D:ProgramsR-2.14.0binRScript —vanilla —no-save —slave query_script.R ’ htmlx]);

This will return a bunch of junk that you won’t need to use, as well as the tweets/followers/friends whatever you have requested in your properly-formed htmlx variable, passed as an argument to, and parsed by, R.

8. I won’t go into the details of how you can then strip the results of this call to produce what you might be looking for because this depends on the specific API calls you are making. As for me, I have created a miniature library that implements specific API calls, and then devours the results using simple regular expressions to produce structures for the returned tweets and users.

I am unlikely to make the rest of the code for this public in the near future and I don’t plan to answer questions about this [because there are experts who will be able to do a much better job than I can] but if you decide you really need to contact me, then it is not terribly difficult to find my email address, or you can tweet me at @adamgdunn.

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