Bug in time_response_plot for multiple responses + improvements in input/output colors. #1171
Description
The following code should work, but generates an error:
import numpy as np
import control as ct
sys = ct.ss(ct.tf([1, 2], [3, 4, 5]))
timepts = np.linspace(0, 10)
resp1 = ct.input_output_response(sys, timepts, np.sin(timepts))
resp2 = ct.input_output_response(sys, timepts, np.cos(timepts))
ct.time_response_plot([resp1, resp2])
Output:
File ~/Library/CloudStorage/Dropbox/macosx/src/python-control/murrayrm/control/timeplot.py:210, in time_response_plot(data, ax, plot_inputs, plot_outputs, transpose, overlay_traces, overlay_signals, add_initial_zero, label, trace_labels, title, relabel, *fmt, **kwargs)
208 # Determine whether or not to plot the input data (and how)
209 if plot_inputs is None:
--> 210 plot_inputs = data.plot_inputs
211 if plot_inputs not in [True, False, 'overlay']:
212 raise ValueError(f"unrecognized value: {plot_inputs=}")
AttributeError: 'list' object has no attribute 'plot_inputs'
Attempting to fixing the error manually, I tried:
ct.time_response_plot([resp1, resp2], plot_inputs=True)
which generated another error:
File ~/Library/CloudStorage/Dropbox/macosx/src/python-control/murrayrm/control/timeplot.py:266, in time_response_plot(data, ax, plot_inputs, plot_outputs, transpose, overlay_traces, overlay_signals, add_initial_zero, label, trace_labels, title, relabel, *fmt, **kwargs)
212 raise ValueError(f"unrecognized value: {plot_inputs=}")
214 #
215 # Find/create axes
216 #
(...)
264
265 # Decide on the number of inputs and outputs
--> 266 ninputs = data.ninputs if plot_inputs else 0
267 noutputs = data.noutputs if plot_outputs else 0
268 ntraces = max(1, data.ntraces) # treat data.ntraces == 0 as 1 trace
AttributeError: 'list' object has no attribute 'ninputs'
Those should be fairly easy to fix. While doing so, it might be nice to think through the color and labeling scheme as well. Using the following commands generates the desired plot, but the labeling is confusing:
resp1.plot()
resp2.plot()
What I would have expected here is that the colors of the traces in the top and bottom panels would be the same, so that you could figure out which went with which.
Of course, there are other situations for which one wants different colors in the inputs and outputs, for example for a MIMO system:
sys_mimo = ct.rss(4, 2, 2)
resp = ct.input_output_response(sys_mimo, timepts, [np.sin(timepts), np.cos(timepts)])
resp.plot(overlay_signal=True)
which generates
Here the output and input traces all have different colors because there is no reason to associate output