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recalculate loci for sisotool and rlocus on axis scaling #1153

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Merged

murrayrm merged 1 commit into python-control:main from repagh:zoom-rlocus

Jun 21, 2025

+95 −9

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recalculate loci for sisotool and rlocus on axis scaling #1153

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recalculate loci for sisotool and rlocus on axis scaling

repagh Jun 4, 2025

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40 changes: 40 additions & 0 deletions 40 control/pzmap.py

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -124,6 +124,17 @@ def plot(self, args, *kwargs):
		"""
		return pole_zero_plot(self, args, *kwargs)

		def replot(self, cplt: ControlPlot):
		"""Update the pole/zero loci of an existing plot.

		Parameters
		----------
		cplt: ControlPlot
		Graphics handles of the existing plot.
		"""
		pole_zero_replot(self, cplt)



		# Pole/zero map
		def pole_zero_map(sysdata):
Expand Down Expand Up		@@ -513,6 +524,35 @@ def _click_dispatcher(event):
		return ControlPlot(out, ax, fig, legend=legend)


		def pole_zero_replot(pzmap_responses, cplt):
		"""Update the loci of a plot after zooming/panning.

		Parameters
		----------
		pzmap_responses : PoleZeroMap list
		Responses to update.
		cplt : ControlPlot
		Collection of plot handles.
		"""

		for idx, response in enumerate(pzmap_responses):

		# remove the old data
		for l in cplt.lines[idx, 2]:
		l.set_data([], [])

		# update the line data
		if response.loci is not None:

		for il, locus in enumerate(response.loci.transpose()):
		try:
		cplt.lines[idx,2][il].set_data(real(locus), imag(locus))
		except IndexError:
		# not expected, but more lines apparently needed
		cplt.lines[idx,2].append(cplt.ax[0,0].plot(
		real(locus), imag(locus)))


		# Utility function to find gain corresponding to a click event
		def _find_root_locus_gain(event, sys, ax):
		# Get the current axis limits to set various thresholds
Expand Down

49 changes: 46 additions & 3 deletions 49 control/rlocus.py

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -33,7 +33,7 @@


		# Root locus map
		def root_locus_map(sysdata, gains=None):
		def root_locus_map(sysdata, gains=None, xlim=None, ylim=None):
		"""Compute the root locus map for an LTI system.

		Calculate the root locus by finding the roots of 1 + k * G(s) where G
Expand All		@@ -46,6 +46,10 @@ def root_locus_map(sysdata, gains=None):
		gains : array_like, optional
		Gains to use in computing plot of closed-loop poles. If not given,
		gains are chosen to include the main features of the root locus map.
		xlim : tuple or list, optional
		Set limits of x axis (see `matplotlib.axes.Axes.set_xlim`).
		ylim : tuple or list, optional
		Set limits of y axis (see `matplotlib.axes.Axes.set_ylim`).

		Returns
		-------
Expand Down Expand Up		@@ -75,7 +79,7 @@ def root_locus_map(sysdata, gains=None):
		nump, denp = _systopoly1d(sys[0, 0])

		if gains is None:
		kvect, root_array, _, _ = _default_gains(nump, denp, None, None)
		kvect, root_array, _, _ = _default_gains(nump, denp, xlim, ylim)
		else:
		kvect = np.atleast_1d(gains)
		root_array = _RLFindRoots(nump, denp, kvect)
Expand Down Expand Up		@@ -205,13 +209,52 @@ def root_locus_plot(
		# Plot the root loci
		cplt = responses.plot(grid=grid, **kwargs)

		# Add a reaction to axis scale changes, if given LTI systems, and
		# there is no set of pre-defined gains
		if gains is None:
		add_loci_recalculate(sysdata, cplt, cplt.axes[0,0])
Comment thread Copilot AI Jun 6, 2025 Copy link There was a problem hiding this comment. Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. [nitpick] Recalculating the entire locus on every `xlim`/`ylim` change can be expensive. Consider debouncing these callbacks or limiting the update frequency during continuous zooming. Sorry, something went wrong. Uh oh! There was an error while loading. Please reload this page. All reactions Copilot uses AI. Check for mistakes. repagh Jun 6, 2025 Copy link Copy Markdown Member Author There was a problem hiding this comment. Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. This was no issue when interacting with the root-locus plot. Default number of points calculate is a measly 50, with the adaptive code in `_default_gains` typically a maximum between 100 and 200 points was produced. The callback will not be activated when the user manually specifies the gains. Sorry, something went wrong. Uh oh! There was an error while loading. Please reload this page. All reactions

		# Legacy processing: return locations of poles and zeros as a tuple
		if plot is True:
		return responses.loci, responses.gains

		return ControlPlot(cplt.lines, cplt.axes, cplt.figure)


		def add_loci_recalculate(sysdata, cplt, axis):
		"""Add a callback to re-calculate the loci data fitting a zoom action.

		Parameters
		----------
		sysdata: LTI object or list
		Linear input/output systems (SISO only, for now).
		cplt: ControlPlot
		Collection of plot handles.
		axis: matplotlib.axes.Axis
		Axis on which callbacks are installed.
		"""

		# if LTI, treat everything as a list of lti
		if isinstance(sysdata, LTI):
		sysdata = [sysdata]

		# check that we can actually recalculate the loci
		if isinstance(sysdata, list) and all(
		[isinstance(sys, LTI) for sys in sysdata]):

		# callback function for axis change (zoom, pan) events
		# captures the sysdata object and cplt
		def _zoom_adapter(_ax):
		newresp = root_locus_map(sysdata, None,
		_ax.get_xlim(),
		_ax.get_ylim())
		newresp.replot(cplt)

		# connect the callback to axis changes
		axis.callbacks.connect('xlim_changed', _zoom_adapter)
		axis.callbacks.connect('ylim_changed', _zoom_adapter)


		def _default_gains(num, den, xlim, ylim):
		"""Unsupervised gains calculation for root locus plot.

Expand Down Expand Up		@@ -288,7 +331,7 @@ def _default_gains(num, den, xlim, ylim):
		# Root locus is on imaginary axis (rare), use just y distance
		tolerance = y_tolerance
		elif y_tolerance == 0:
		# Root locus is on imaginary axis (common), use just x distance
		# Root locus is on real axis (common), use just x distance
		tolerance = x_tolerance
		else:
		tolerance = np.min([x_tolerance, y_tolerance])
Expand Down

15 changes: 9 additions & 6 deletions 15 control/sisotool.py

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Original file line number Diff line number Diff line change

Expand Up @@ -22,6 +22,7 @@

from .statesp import ss, summing_junction

from .timeresp import step_response

from .xferfcn import tf

from .rlocus import add_loci_recalculate

_sisotool_defaults = {

'sisotool.initial_gain': 1

Expand Down Expand Up @@ -105,7 +106,7 @@ def sisotool(sys, initial_gain=None, xlim_rlocus=None, ylim_rlocus=None,

fig = plt.gcf()

if fig.canvas.manager.get_window_title() != 'Sisotool':

plt.close(fig)

fig,axes = plt.subplots(2, 2)

fig, axes = plt.subplots(2, 2)

fig.canvas.manager.set_window_title('Sisotool')

else:

axes = np.array(fig.get_axes()).reshape(2, 2)

Expand Down Expand Up @@ -137,15 +138,18 @@ def sisotool(sys, initial_gain=None, xlim_rlocus=None, ylim_rlocus=None,

# sys[0, 0], initial_gain=initial_gain, xlim=xlim_rlocus,

# ylim=ylim_rlocus, plotstr=plotstr_rlocus, grid=rlocus_grid,

# ax=fig.axes[1])

ax_rlocus = fig.axes[1]

root_locus_map(sys[0, 0]).plot(

ax_rlocus = axes[0,1] # fig.axes[1]

cplt = root_locus_map(sys[0, 0]).plot(

xlim=xlim_rlocus, ylim=ylim_rlocus,

initial_gain=initial_gain, ax=ax_rlocus)

if rlocus_grid is False:

# Need to generate grid manually, since root_locus_plot() won't

from .grid import nogrid

nogrid(sys.dt, ax=ax_rlocus)

# install a zoom callback on the root-locus axis

add_loci_recalculate(sys, cplt, ax_rlocus)

# Reset the button release callback so that we can update all plots

fig.canvas.mpl_connect(

'button_release_event', partial(

Expand All @@ -155,9 +159,8 @@ def sisotool(sys, initial_gain=None, xlim_rlocus=None, ylim_rlocus=None,

def _click_dispatcher(event, sys, ax, bode_plot_params, tvect):

# Zoom handled by specialized callback in rlocus, only handle gain plot

if event.inaxes == ax.axes and \

plt.get_current_fig_manager().toolbar.mode not in \

{'zoom rect', 'pan/zoom'}:

if event.inaxes == ax.axes:

fig = ax.figure

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Comment on lines +162 to 165

Copilot AI Jun 6, 2025

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[nitpick] The original toolbar mode check for 'zoom rect' and 'pan/zoom' was removed, which may trigger click events during zooming or panning. Consider re-adding that guard to prevent unintended callbacks.

Suggested change

	if event.inaxes == ax.axes:

	fig = ax.figure
	fig = ax.figure
	toolbar = fig.canvas.toolbar
	if toolbar is not None and toolbar.mode in ['zoom rect', 'pan/zoom']:
	return
	if event.inaxes == ax.axes:

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Copilot uses AI. Check for mistakes.

repagh Jun 6, 2025

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In my experience, the risk of interpreting a click as a valid gain selection is small, and in my testing (with a print statement indicating when the callback is invoked), the zoom and pan events did not propagate to this callback. Removing the zoom_rect and pan/zoom check also removes unintended mode change (updating of the remaining 3 plots is inhibited when zoom / pan is selected), which can be confusing to users.

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# if a point is clicked on the rootlocus plot visually emphasize it

Expand Down

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