Add hsu soiling model gallery example.

[jsstein]

• [x ] Closes Add hsu soiling model example #989
• [x ] I am familiar with the contributing guidelines
• Tests added
• Updates entries to docs/sphinx/source/api.rst for API changes.
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels and Milestone are assigned to the Pull Request and linked Issue.

[jsstein]

This is my first gallery example, I am not sure if I did it right. I followed other examples the best I could, but I was unable to figure out how to check how the figures look. Any suggestions on how to do that? Thanks!

It should look like this:

followed by this image from the original paper:

[kandersolar]

I think examples that recreate figures from the reference paper are a good idea. It's another layer of tests, in a way.

For seeing if the example script works as expected, you have two options:

• The documentation gets rebuilt as one of the automatic checks that run whenever a PR is updated, it's listed as "docs/readthedocs.org" in the list of checks (it takes a few minutes to complete after an update). Here's the output for this PR: https://pvlib-python--990.org.readthedocs.build/en/990/auto_examples/plot_fig3A_hsu_soiling_example.html
• It's also possible to do a local build with your copy of the repository following the instructions in this unmerged PR: https://github.com/pvlib/pvlib-python/pull/982/files

[jsstein]

I have no idea why "(1,2)" shows up in front of the reference. on the doc page: [https://pvlib-python--990.org.readthedocs.build/en/990/auto_examples/plot_fig3A_hsu_soiling_example.html] Any ideas?

[kandersolar]

Here are some quick notes. It would be cool to also recreate Figure 4, but that would need the PRISM dataset as well.

[kandersolar]

I have no idea why "(1,2)" shows up in front of the reference. on the doc page: [https://pvlib-python--990.org.readthedocs.build/en/990/auto_examples/plot_fig3A_hsu_soiling_example.html] Any ideas?

This is a recurring point of confusion :) It's because we're using footnotes for references. Those are links to the places in the text where that citation is referenced. It's referenced in two places, so it links them as a list (1,2). It's a little strange, but that output is (for now) the right way to do it.

[cwhanse]

thanks @jsstein and @kanderso-nrel