System norms 2

[henriks76]

I believe all earlier feedback on sysnorm.py has been addressed now.

[bnavigator]

See #960 (comment)

Please don't restrict the tolerance to 1e-9. It will create problems like the one solved in #366.

[henriks76]

Is it OK to set the default to 1e-2? (For comparison: statesp.linfnorm uses default tolerance 1e-10, and MATLAB's hinfnorm uses 1e-2.)

[bnavigator]

That's maybe a bit coarse. I'd say we start with 1e-6 and see if we get failures, e.g. in distribution packages like the openSUSE rpm or conda after the next release.

[bnavigator]

I have fixed the futurewarning test. Please rebase.

[coveralls]

coverage: 94.422% (-0.4%) from 94.784%
when pulling bad229a on henriks76:system-norms
into af4f8a7 on python-control:main.

[bnavigator]

Thank you @henriks76!

[KybernetikJo]

Thank you @henriks76. I also had plans to implement the norm() method. That's why I was interested in Slycot.ab13bd and Slycot.ab13dd in the first place.

You might want to add the method norm to the function reference in the sphinx documentation. Otherwise, the norm() method is hard to find.

https://github.com/python-control/python-control/blob/main/doc/control.rst
I guess the right place would be Utility functions and conversions after modal_form.

A new PR would be the right way.

[henriks76]

Thanks, @KybernetikJo and @bnavigator, for all the excellent feedback! I'll look into the documentation as soon as possible.

[henriks76]

Is it correct that the sphinx documentation will be automatically generated from the function docstring, or would you like me to copy it somewhere? This is all very new to me...

I have already tried to follow the conventions here, but let me know if something needs fixing.

[KybernetikJo]

Is it correct that the sphinx documentation will be automatically generated from the function docstring, or would you like me to copy it somewhere? This is all very new to me...

No need to copy anything for API documentation, you only have to add your method to
https://github.com/python-control/python-control/blob/main/doc/control.rst

....
modal_form
norm # <-- your method
observable_form
...

The autosummary of sphinx should take care about your API documentation.

You have to install all requirements (https://github.com/python-control/python-control/blob/main/doc/requirements.txt) for sphinx (e.g. with pip)

pip install -r doc/requirements.txt

and then you run the bash command in the doc folder

make html

You can follow the instructions, point 6.
https://github.com/python-control/python-control/wiki/How-to-contribute-with-a-pull-request

---

I have already tried to follow the conventions here, but let me know if something needs fixing.

I only skimmed over it, but it looks good to me.
We can take care about that later in your PR.