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Slightly more Details

You want to contribute? Awesome! Small changes, like fixing typos in documentation are completely fine and also most welcome. For bigger changes, we suggest that you open an issue before you start coding, so that we can maximize the probability that we can successfully merge in your code.

R or C

This guide is for the igraph R package, but note that the package uses the igraph C library internally for most things. If your changes involve the C library as well, then you need to make those changes first, in the repository of the C library:

Development and Compilation

All development is being done on the default branch so that it can be automatically installed using remotes::install_github("igraph/rigraph") or pak::pak("igraph/rigraph"). If you have the stable version of igraph already installed, you can avoid conflicts by installing the development version in its own directory, e.g. remotes::install_github("igraph/rigraph", lib = "~/testing/"). Then, to load the development version in an R session, use library(igraph, lib.loc = "~/testing/"). Remove the development version with remove.packages("igraph", lib = "~/testing/").

You can locally build and test the igraph package as follows. From an R process running in the local ./rigraph directory, run pkgload::load_all() to compile the cloned version of igraph and load it for use in the current session. You can run the package tests with testthat::test_local(). If your change includes updates to the documentation, also run devtools::document() to update the package documentation. Note that you can either clone the package and locally build it with pkgload::load_all() or install the package from GitHub with remotes::install_github()—you do not need to do both. You can keep your local clone up to date with git tools, or remove it by deleting the local ./rigraph directory.


When building from source on Windows, you need to have RTools installed. Additionally, the two system requirements of glpk and libxml2 are not optional, but hard requirements. For version R >= 4.0 you can install these two from an RTools terminal using

pacman -Sy mingw-w64-{i686,x86_64}-glpk mingw-w64-{i686,x86_64}-libxml2

To update the files stored redundantly, run

make igraph

. This is done automatically on CI/CD, in some cases changes are committed directly to the branch that is being tested.

Making Trivial Changes

  • Fork the repository. You should have a copy of /rigraph under your username, at<username>/rigraph.
  • In your forked repository, look for the file you want to modify.
  • Click on the edit symbol (pen) on the upper right corner of the file view.
  • Make your edits.
  • Write a short commit message, less than 65 characters. E.g. “Fix manual page typo” or “Fix degree bug for loops”. If needed, elaborate your changes below in the “extended description” field.
  • Commit your changes.
  • Go back to the start page of your forked repository.
  • Click on the green button before the branch name to create a pull request.
  • Click on “Create pull request”.
  • Provide a more detailed description if you like. Please also indicate that you are fine with licensing your contribution under igraph’s license (see Legal Stuff below).
  • Click on “Create pull request”.
  • That’s it! It is probably a good idea to keep your forked repository until the change is accepted into igraph, in case you need to modify it.
  • Now you need to wait for us, unfortunately. Please ping us, if it takes long to respond. E.g. a week is considered to be long.
  • Once your pull request is accepted, you can delete your forked repository.

Making More Involved Changes

This is mostly the same as for trivial changes, but you probably want to edit the sources on your computer, instead of online on GitHub. If you are unfamiliar with cloning repositories from GitHub, the manual page for working with remote repositories is a good place to start. There is also a more general introduction page here, which includes information on setting up git. The git manual is here. R development environments may also include support for git/GitHub integration (for an introduction to the RStudio tools, see this tutorial; Emacs/ESS users can use Magit).

  • Open an issue in the issue tracker about the proposed changes. This is not required for smaller things, but we suggest you do it for others. Just in case somebody is already working on the same thing, or it is something we don’t want in igraph.
  • Fork and clone the repository. If you have already forked the repository, synch your forked copy to get the latest version of the main branch, then fetch the updated main to your local clone.
  • Make changes to the appropriate files in the local clone.
  • Once ready with your changes, build igraph and run the tests as indicated above.
  • Commit your changes to a new branch. Give the branch a descriptive name that is specific to the changes you want to make. Then, push those changes to your forked copy of igraph on GitHub.
  • Submit your pull request to the main branch. You should see text similar to “<username> wants to merge 1 commit into igraph:main from <username>:fix-some-func”. If your pull request relates directly to an issue (e.g., if you opened an issue to discuss the proposed changes), include the keyword “fix” and the issue number (e.g., “Fix #123) on its own line in your initial comment for the pull request. This step supports better issue tracking; for a list of keywords, see here.
  • Now you need to wait for us, unfortunately. Please ping us, if it takes long to respond. E.g. a week is considered to be long.

Writing igraph Code

Some tips on writing igraph code. In general, look at how things are done, and try to do them similarly. (Unless you think they are not done well, in which case please tell us.)

Code Formatting

We follow the tidyverse style guide for formatting. The styler package helps apply this style to the code (see also the lintr package). Look at the style (indentation, braces, etc.) of some recently committed bigger change, and try to mimic that.


Please document your new functions using roxygen2, and run devtools::document() or make igraph to update the .Rd files.

Test Cases

Unless you change something trivial, please consider adding test cases. This is important! See the files in the ./rigraph/tests/testthat directory for examples. See the r-utils package testthat for some unit testing support functions.

Ask Us!

In general, if you are not sure about something, please ask! You can open an issue on Github, write to the igraph-help mailing list (see the homepage at, or write to Tamás and Gábor. We prefer the public forums, though, because then others can learn from it, too.

This is a pain to deal with, but we can’t avoid it, unfortunately. So, igraph is licensed under the “General Public License (GPL) version 2, or later”. The igraph manual is licensed under the “GNU Free Documentation License”. If your contribution is bigger than a typo fix, then please indicate that you are fine with releasing your code/text under these licenses. E.g. adding a sentence that reads as “I’m fine with GPL 2 or later and FDL.” is perfectly enough.