diff --git a/control/frdata.py b/control/frdata.py
index 1bdf28528..ac032d3f7 100644
--- a/control/frdata.py
+++ b/control/frdata.py
@@ -261,6 +261,11 @@ def __init__(self, *args, **kwargs):
# create interpolation functions
if smooth:
+ # Set the order of the fit
+ if self.omega.size < 2:
+ raise ValueError("can't smooth with only 1 frequency")
+ degree = 3 if self.omega.size > 3 else self.omega.size - 1
+
self.ifunc = empty((self.fresp.shape[0], self.fresp.shape[1]),
dtype=tuple)
for i in range(self.fresp.shape[0]):
@@ -268,7 +273,8 @@ def __init__(self, *args, **kwargs):
self.ifunc[i, j], u = splprep(
u=self.omega, x=[real(self.fresp[i, j, :]),
imag(self.fresp[i, j, :])],
- w=1.0/(absolute(self.fresp[i, j, :]) + 0.001), s=0.0)
+ w=1.0/(absolute(self.fresp[i, j, :]) + 0.001),
+ s=0.0, k=degree)
else:
self.ifunc = None
@@ -392,7 +398,12 @@ def __add__(self, other):
# Convert the second argument to a frequency response function.
# or re-base the frd to the current omega (if needed)
- other = _convert_to_frd(other, omega=self.omega)
+ if isinstance(other, (int, float, complex, np.number)):
+ other = _convert_to_frd(
+ other, omega=self.omega,
+ inputs=self.ninputs, outputs=self.noutputs)
+ else:
+ other = _convert_to_frd(other, omega=self.omega)
# Check that the input-output sizes are consistent.
if self.ninputs != other.ninputs:
diff --git a/control/tests/lti_test.py b/control/tests/lti_test.py
index 3f001c17b..5359ceea3 100644
--- a/control/tests/lti_test.py
+++ b/control/tests/lti_test.py
@@ -350,3 +350,21 @@ def test_subsys_indexing(fcn, outdx, inpdx, key):
np.testing.assert_almost_equal(
subsys_fcn.frequency_response(omega).response,
subsys_chk.frequency_response(omega).response)
+
+
+@slycotonly
+@pytest.mark.parametrize("op", [
+ '__mul__', '__rmul__', '__add__', '__radd__', '__sub__', '__rsub__'])
+@pytest.mark.parametrize("fcn", [ct.ss, ct.tf, ct.frd])
+def test_scalar_algebra(op, fcn):
+ sys_ss = ct.rss(4, 2, 2)
+ match fcn:
+ case ct.ss:
+ sys = sys_ss
+ case ct.tf:
+ sys = ct.tf(sys_ss)
+ case ct.frd:
+ sys = ct.frd(sys_ss, [0.1, 1, 10])
+
+ scaled = getattr(sys, op)(2)
+ np.testing.assert_almost_equal(getattr(sys(1j), op)(2), scaled(1j))
diff --git a/control/xferfcn.py b/control/xferfcn.py
index 56ec7395f..5304ea636 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -634,11 +634,11 @@ def __mul__(self, other):
from .statesp import StateSpace
# Convert the second argument to a transfer function.
- if isinstance(other, StateSpace):
+ if isinstance(other, (StateSpace, np.ndarray)):
other = _convert_to_transfer_function(other)
- elif isinstance(other, (int, float, complex, np.number, np.ndarray)):
- other = _convert_to_transfer_function(other, inputs=self.ninputs,
- outputs=self.noutputs)
+ elif isinstance(other, (int, float, complex, np.number)):
+ # Multiply by a scaled identity matrix (transfer function)
+ other = _convert_to_transfer_function(np.eye(self.ninputs) * other)
if not isinstance(other, TransferFunction):
return NotImplemented
@@ -681,8 +681,8 @@ def __rmul__(self, other):
# Convert the second argument to a transfer function.
if isinstance(other, (int, float, complex, np.number)):
- other = _convert_to_transfer_function(other, inputs=self.ninputs,
- outputs=self.ninputs)
+ # Multiply by a scaled identity matrix (transfer function)
+ other = _convert_to_transfer_function(np.eye(self.noutputs) * other)
else:
other = _convert_to_transfer_function(other)
@@ -723,9 +723,8 @@ def __truediv__(self, other):
"""Divide two LTI objects."""
if isinstance(other, (int, float, complex, np.number)):
- other = _convert_to_transfer_function(
- other, inputs=self.ninputs,
- outputs=self.ninputs)
+ # Multiply by a scaled identity matrix (transfer function)
+ other = _convert_to_transfer_function(np.eye(self.ninputs) * other)
else:
other = _convert_to_transfer_function(other)
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