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Fix zero-input interconnect D matrix shape #1221

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Merged
murrayrm merged 1 commit into from
Jun 8, 2026
Merged

Fix zero-input interconnect D matrix shape #1221

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8 changes: 4 additions & 4 deletions control/statesp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2295,7 +2295,7 @@ def _ssmatrix(data, axis=1, square=None, rows=None, cols=None, name=None):

Returns
-------
arr : 2D array, with shape (0, 0) if a is empty
arr : 2D array, with shape (0, 0) for empty vectors or matrices

"""
# Process the name of the object, if available
Expand All @@ -2310,9 +2310,9 @@ def _ssmatrix(data, axis=1, square=None, rows=None, cols=None, name=None):
if (ndim > 2):
raise ValueError(f"state-space matrix{name} must be 2-dimensional")

elif (ndim == 2 and shape == (1, 0)) or \
(ndim == 1 and shape == (0, )):
# Passed an empty matrix or empty vector; change shape to (0, 0)
elif (ndim == 2 and shape == (0, 0)) or \
(ndim == 1 and shape == (0, )):
# Passed a 0-by-0 matrix or empty vector; change shape to (0, 0)
shape = (0, 0)

elif ndim == 1:
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30 changes: 30 additions & 0 deletions control/tests/interconnect_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -432,6 +432,36 @@ def test_linear_interconnect():
outlist=['plant.y'], outputs='y')
assert clsys.syslist[0].name == 'ctrl'


def test_interconnect_zero_input_one_output():
plant = ct.ss(
[[1, 1], [0, -2]],
[[0], [1]],
[[1, 0]],
[[0]],
inputs=['u'],
outputs=['y'],
name='plant',
dt=True,
)
controller = ct.ss(
[[2.25, 1], [-5, -0.5]],
[[-1.25], [4.5]],
[[-0.5, 1.5]],
[[0]],
inputs=['y'],
outputs=['u'],
name='controller',
dt=True,
)

sys = ct.interconnect([plant, controller], inplist=None, outlist=['y'])

assert sys.ninputs == 0
assert sys.noutputs == 1
assert sys.D.shape == (1, 0)


@pytest.mark.parametrize(
"connections, inplist, outlist, inputs, outputs", [
pytest.param(
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