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FIX: Accept precomputed responses in gangof4_plot #1261

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FIX: Accept precomputed responses in gangof4_plot #1261

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8644bd2
fix(freqplot): accept precomputed gang-of-four responses
huxiaoyi-ovo Oct 27, 2026
5319822
test(freqplot): cover precomputed gang-of-four plots and options
huxiaoyi-ovo Oct 27, 2026
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5 changes: 2 additions & 3 deletions control/freqplot.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2311,12 +2311,11 @@ def gangof4_plot(

"""
if len(args) == 1 and isinstance(args[0], FrequencyResponseData):
if any([kw is not None
for kw in [omega, omega_limits, omega_num, Hz]]):
if any(kw is not None for kw in [omega, omega_limits, omega_num]) or Hz:
raise ValueError(
"omega, omega_limits, omega_num, Hz not allowed when "
"given a Gang of 4 response as first argument")
return args[0].plot(kwargs)
return args[0].plot(**kwargs)
else:
if len(args) > 3:
raise TypeError(
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43 changes: 43 additions & 0 deletions control/tests/freqplot_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -258,6 +258,49 @@ def test_gangof4_plots(savefigs=False):
plt.savefig('freqplot-gangof4.png')



@pytest.mark.usefixtures("mplcleanup")
def test_gangof4_plot_precomputed_response():
"""A precomputed response must use the same 2x2 plot API as P/C input."""
P = ct.tf([1], [1, 1], name="P")
C = ct.tf([2], [1], name="C")
response = ct.gangof4_response(P, C, omega=np.logspace(-2, 2, 16))

cplt = ct.gangof4_plot(response, dB=True)

assert cplt.axes.shape == (2, 2)
assert all(len(lines) > 0 for lines in cplt.lines.flat)


def test_gangof4_plot_precomputed_passes_kwargs(monkeypatch):
"""Plot options must be forwarded as keywords, not a positional dict."""
response = ct.gangof4_response(ct.tf([1], [1, 1]), ct.tf([2], [1]))
seen = {}
sentinel = object()

def check_plot(*args, **kwargs):
assert not args
seen.update(kwargs)
return sentinel

monkeypatch.setattr(response, "plot", check_plot)
assert ct.gangof4_plot(response, dB=True, label="closed loop", Hz=False) is sentinel
assert seen == {"dB": True, "label": "closed loop"}


@pytest.mark.parametrize("frequency_kwargs", [
{"omega": np.array([1.0, 2.0])},
{"omega_limits": [0.1, 10]},
{"omega_num": 100},
{"Hz": True},
])
def test_gangof4_plot_precomputed_rejects_frequency_kwargs(frequency_kwargs):
"""A response with fixed frequencies cannot select them again."""
response = ct.gangof4_response(ct.tf([1], [1, 1]), ct.tf([2], [1]))
with pytest.raises(ValueError, match="not allowed"):
ct.gangof4_plot(response, **frequency_kwargs)


@pytest.mark.parametrize("response_cmd, return_type", [
(ct.frequency_response, ct.FrequencyResponseData),
(ct.nyquist_response, ct.freqplot.NyquistResponseData),
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