Create latex output for Jupyter notebooks

PR #276 adds latex output for transfer functions. It would be nice to add this for other LTI types as well (particularly StateSpace objects). Having the output match the text approximation in __repr__ seems like a good first cut at format to use.

[roryyorke]

Having Jupyter display the Mathjax is useful for small state spaces, but I’ve had some problems with larger ones causing Jupyter Notebook to hang. I then have to forcibly stop my browser and then reopening, hoping that I can clear all outputs before it starts rendering.

A short-term workaround is to remove the related method after importing python-control:

import control as ct
del ct.statesp.StateSpace._repr_latex_

Using display(ss) to show the Mathjax version might be more appropriate,

My understanding is that display just a way to force output of a variable, so IPython cells

a = ss(1,2,3,4);
display(a)

and

a = ss(1,2,3,4)
a

are equivalent.

A switch back to “plain old repr” for bigger systems seems like a reasonable idea. We could add a config.defaults['statesp.latex_maxsize'] and if either (nstates + ninputs) or (nstate + noutputs) > latex_maxsize, have _repr_latex_ return None. One could then set latex_maxsize to -1 to disable the LaTeX display altogether. See https://ipython.readthedocs.io/en/stable/config/integrating.html

[roryyorke]

Branch and gist updated. User can select from ‘partitioned’ and ‘separate’ types, and specify format string.

Static-gain (“stateless”) systems are special-cased.

How should configuration options be documented?

I think this should have some minimal testing, though I’ll probably use a “gold image” approach, i.e., generate reference strings using the implementation.