Thanks to visit codestin.com
Credit goes to github.com

Skip to content

recalculate loci for sisotool and rlocus on axis scaling #1153

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Jun 21, 2025
Merged

recalculate loci for sisotool and rlocus on axis scaling #1153

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
40 changes: 40 additions & 0 deletions control/pzmap.py
View file
Open in desktop
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 control/rlocus.py
View file
Open in desktop
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])
Copy link
Preview

Copilot AI Jun 6, 2025

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.

Copilot uses AI. Check for mistakes.

Copy link
Member Author

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.


# 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 control/sisotool.py
View file
Open in desktop
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

Comment on lines +162 to 165
Copy link
Preview

Copilot AI Jun 6, 2025

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

[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:

Copilot uses AI. Check for mistakes.

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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.

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