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Feedback and Contribution

We welcome any input, feedback, bug reports, and contributions via Altair's GitHub Repository. In particular, we welcome companion efforts from other visualization libraries to render the Vega-Lite specifications output by Altair. We see this portion of the effort as much bigger than Altair itself: the Vega and Vega-Lite specifications are perhaps the best existing candidates for a principled lingua franca of data visualization.

We are also seeking contributions of additional Jupyter notebook-based examples in our separate GitHub repository: https://github.com/altair-viz/altair_notebooks.

The altair users mailing list can be found at https://groups.google.com/forum/#!forum/altair-viz. If you are working on Altair, you can talk to other developers in the #altair channel of the Vega slack.

Adding Examples

We are always interested in new examples contributed from the community. These could be everything from simple one-panel scatter and line plots, to more complicated layered or stacked plots, to more advanced interactive features. Before submitting a new example check the Altair Example Gallery to make sure that your idea has not already been implemented.

Once you have an example you would like to add there are a few guide lines to follow. Every example should:

  • be saved as a stand alone script in the altair/examples/ directory.
  • have a descriptive docstring, which will eventually be extracted for the documentation website.
  • contain a category tag.
  • define a chart variable with the main chart object (This will be used both in the unit tests to confirm that the example executes properly, and also eventually used to display the visualization on the documentation website).
  • not make any external calls to download data within the script (i.e. don't use urllib). You can define your data directly within the example file, generate your data using pandas and numpy, or you can use data available in the vega_datasets package.

The easiest way to get started would be to adapt examples from the Vega-Lite example gallery which are missing in the altair gallery. Or you can feel free to be creative and build your own visualizations.

Initial Setup

Install the latest version of Altair locally using

pip install git+https://github.com/altair-viz/altair/

Next step is to fork the repository on GitHub and clone the fork to you local machine. For more details on forking see the GitHub Documentation.

git clone https://github.com/YOUR-USERNAME/altair.git

You can have a single clone of the repository that points to both your fork and the main package repository. These pointers to GitHub are called "remotes" . On your local clone you should run:

git remote add upstream https://github.com/altair-viz/altair.git
git checkout master
git pull upstream master

And then you'll have all the updates in the master branch of your local fork. Note that git will complain if you've committed changes to your local master branch that are not on upstream (this is one reason it's good practice to never work directly on your master branch).

Steps to Contribute

Often it is convenient to draft an example outside of the main repository, such as Google Colab, to avoid difficulties when working with git. Once you have an example you would like to add the procedure is to first update your master branch.

git checkout master
git pull upstream master

Then create a branch for your example submission

git checkout -b <branch-name>

Now you are on a new branch where you can add your example file. All examples files are kept in the altair/examples/ directory. Make sure the style and format match the other examples. An official style guide for examples has not been created yet, but a few suggestions are

  • The file docstring will be rendered into HTML via reStructuredText, so use that format for any hyperlinks or text styling. In particular, be sure you include a title in the docstring underlined with ---, and be sure that the size of the underline exactly matches the size of the title text.
  • If your example fits into a chart type but involves significant configuration it should be in the case studies category. If your example doesn't fit well into any category then it can be included in the other charts category.
  • For consistency all data used for a visualization should be assigned to the variable source. Then source is passed to the alt.Chart object. See other examples for guidance.
  • If you are using the vega_datasets package there are multiple ways to refer to a data source. If the dataset you would like to use is included in local installation (vega_datasets.local_data.list_datasets()) then the data can be referenced directly, such as source = data.iris(). If the data is not included then it should be referenced by URL, such as source = data.movies.url. This is to ensure that Altair's automated test suite does not depend on availability of external HTTP resources.

Next step is to commit your example file and push the branch to your forked repo

git add <example.py>
git commit -m 'DOC: Add example for <example>'
git push origin <branch-name>

Finally you will need to submit a pull request (PR) on GitHub asking to merge your example branch into altair master. For details on creating a PR see GitHub documentation Creating a pull request. You can add more details about your example in the PR such as motivation for the example or why you thought it would be a good addition. You will get feed back in the PR discussion if anything needs to be changed. To make changes continue to push commits made in your local example branch to origin and they will be automatically shown in the PR.

Hopefully your PR will be answered in a timely manner and your example will help others in the future. Note that examples shown on the altair website are only updated when a new version is released so your new example might not show up there for a while.