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Use the time axis of transposed inputs in discrete-time forced_response #1255

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Use the time axis of transposed inputs in discrete-time forced_response #1255

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21 changes: 21 additions & 0 deletions control/tests/timeresp_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1255,6 +1255,27 @@ def test_response_transpose(
assert x.shape == (T.size, sys.nstates)


@pytest.mark.parametrize("ninputs", [1, 2])
def test_forced_response_transpose_discrete(ninputs):
# Transposed inputs have time along the first axis, including when the
# time vector is computed from them (gh-931)
sys = ct.rss(3, 2, ninputs, dt=0.1)
U = np.random.default_rng(0).standard_normal((ninputs, 10))

resp = ct.forced_response(sys, U=U, squeeze=False)
resp_t = ct.forced_response(
sys, U=U.T, transpose=True, squeeze=False)
np.testing.assert_equal(resp_t.time, resp.time)
np.testing.assert_allclose(np.transpose(resp_t.outputs), resp.outputs)

# Scalar input with a given time vector
T = np.arange(10) * 0.1
resp = ct.forced_response(sys, T=T, U=1.0, squeeze=False)
resp_t = ct.forced_response(
sys, T=T, U=1.0, transpose=True, squeeze=False)
np.testing.assert_allclose(np.transpose(resp_t.outputs), resp.outputs)


@pytest.mark.pandas
def test_to_pandas():
# Create a SISO time response
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6 changes: 5 additions & 1 deletion control/timeresp.py
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Expand Up @@ -1112,7 +1112,8 @@ def forced_response(
raise ValueError('Parameters `T` and `U` can\'t both be '
'zero for discrete-time simulation')
# Set T to equally spaced samples with same length as U
if U.ndim == 1:
# (time is along the first axis of a transposed U)
if U.ndim == 1 or transpose:
n_steps = U.shape[0]
else:
n_steps = U.shape[1]
Expand All @@ -1121,6 +1122,9 @@ def forced_response(
else:
if U.ndim == 0:
U = np.full((n_inputs, T.shape[0]), U)
if transpose:
# U gets transposed back when its shape is checked
U = U.T
else:
if T is None:
raise ValueError('Parameter `T` is mandatory for continuous '
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