Improvements to Nichols chart plotting#723
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bnavigator merged 5 commits intopython-control:masterfrom Apr 30, 2022
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Clip closed-loop contour labels. Add labels for constant closed-loop phase contours. Use smaller of data or view extents when deciding on how big, in phase, a chart to create. Use more uniformly spaced closed-loop phase contours, and use more widely-spaced contours when phase extent is large. Add optional `ax` argument, for axes to add grid to.
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Changes look good. It might be worth adding some unit tests to cover the new features (eg, use of |
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OK, I'll look at some tests, including testing the I'll probably wrap up the linfnorm PR first, and I'm not sure when I'll get this PR done. |
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I changed nichols_grid to return the artists it adds; this made testing much easier, but also makes it possible to customize the grid appearance and labels. Below is a not-especially-compelling example; more realistically one might change the intensity or alpha of the grid and labels. plt.clf()
mc,nc,ml,nl = ct.nichols_grid()
for i,(c,l) in enumerate(zip(nc,nl)):
nc.set_color(f'C{i}')
nl.set_color(f'C{i}')
for i,(c,l) in enumerate(zip(mc,ml)):
c.set_color(f'C{i}')
l.set_color(f'C{i}')
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bnavigator
reviewed
Apr 27, 2022
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This looks good to go to me. @roryyorke: any additional changes that you plan to make? |
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No, all done.
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This looks good to go to me. @roryyorke <https://github.com/roryyorke>:
any additional changes that you plan to make?
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These are relatively minor updates to the Nichols chart (AKA grid) plotting.
It's far from ideal; further possible improvements:
'xlim_changed'and'ylim_changed'eventsContourSets, and plug into however that labelling is done?Here are some before-and-after pictures (left is before) of a few example systems.
The new code gives a better result in almost all respects. One visible problem is that the closed-loop phase label for "0°" clashes with the "-40dB" (and similar) closed-loop gain label. The gains become crowded when the gain span is large (final figure), but that is the same in both versions.
I haven't added tests; I'll see how much time I have to do that. Easyish tests:
ifin_inner_extents, and in fact test the behaviour in general by setting xlim & ylim before calling nichols_grid.Please suggest other tests.
Details (commit message)
Clip closed-loop contour labels.
Add labels for constant closed-loop phase contours.
Use smaller of data or view extents when deciding on how big, in
phase, a chart to create.
Use more uniformly spaced closed-loop phase contours, and use more
widely-spaced contours when phase extent is large.
Add optional
axargument, for axes to add grid to.