stackr: an R package for connecting to the Stack Exchange API

This R package serves as an unofficial wrapper for the read-only features of the Stack Exchange API with the ability to download information on questions, answers, users, tags, and other aspects of the site so that they can be analyzed in R. It is not affiliated with Stack Exchange.

The documentation of the Stack Exchange API is worth reviewing, as the package is built to resemble that interface while remaining true to R's style and syntax.

Installation

You can install the package with devtools as such:

# install.packages("devtools")
devtools::install_github("dgrtwo/stackr")

# if you want to access the vignettes from within the package:
devtools::install_github("dgrtwo/stackr", build_vignettes = TRUE)
browseVignettes("stackr")

Basics

Methods for querying objects from the APIare implemented in functions of the form stack_[object]. Each of these functions returns a data frame, with one row per object.

For example, one could query recent questions with:

q <- stack_questions()

And recent answers with:

a <- stack_answers()

Almost all of these functions can take as their first argument one or more IDs. For example, one could query a specific question:

stack_questions(11227809)

Or one could query multiple answers using a vector:

stack_answers(c(179147, 2219560, 180085))

Other results you can query include users:

stack_users(712603)

Or tags, which are queried by name instead of id:

stack_tags(c("r", "ggplot2", "dplyr"))

Returned values

Each of these functions returns a data.frame. The columns that are included depend on the object being returned, with documentation available on the Stack Exchange API site:

• answer
• badge
• comment
• info
• post
• privilege
• question
• revision
• suggested-edit
• tags
• user

Special queries

A function like stack_questions does not necessarily return questions. By providing a second argument to the query, one can extract objects that are related to that object. For example, one could extract all the answers to a particular question with:

answers <- stack_questions(11227809, "answers")

Similarly, one could extract the comments, linked questions, or related questions with:

comments <- stack_questions(11227809, "comments")
linked <- stack_questions(11227809, "linked")
related <- stack_questions(11227809, "related")

There are many other combinations: one could extract a user's comments:

my_comments <- stack_users(712603, "comments")

The combinations of methods and actions is best explained in the documentation.

Pagination

You can set the pagesize argument to any method to determine the number of objects to be returned. However, the maximum value of this is 100, which means multiple requests must be made to download a list larger than 100.

stackr handles this pagination with the num_pages argument, which all methods accept. This gives a maximum number of pages (and therefore requests) that will be iterated through, combining them together at the end.

API Key

It's a good idea to set up a registered API key with Stack Exchange, since it increases your daily quota of queries from 300 to 10,000. You can register an app here. Once you have your Stack Exchange application key, set up an environment variable, by adding the following line to your .Rprofile:

Sys.setenv(STACK_EXCHANGE_KEY = "YOUR_KEY_HERE")

After that, queries made from your system will use your key.

Future plans

Currently, no methods requiring authentication are implemented. OAuth 2.0 could be implemented through the same httr framework (see here), but my current judgment is that R is likely to be used for data analysis operations rather than actual front-ends for Stack Exchange, which negates the need for most authentication-based operations.

So far, no network methods (such as "/sites", or "/apps") have yet been implemented; only per-site methods.

Bug reports are very welcome here.