FIX:

forgi86 · forgi86 · commit 9c6870045be0 · 2021-03-31T20:55:49.000+02:00
- in singular_values_plot: the complex argument to be evaluated for the frequency response is now computed in the if branch
- fixed typos in freqresp_test.py: the siso system is now also tested
diff --git a/control/freqplot.py b/control/freqplot.py
@@ -54,7 +54,6 @@
 from .exception import ControlMIMONotImplemented
 from .statesp import StateSpace
 from .xferfcn import TransferFunction
-from .lti import evalfr
 from . import config
 
 __all__ = ['bode_plot', 'nyquist_plot', 'gangof4_plot', 'singular_values_plot',
@@ -1157,10 +1156,12 @@ def singular_values_plot(syslist, omega=None,
                 # limit up to and including nyquist frequency
                 omega_sys = np.hstack((
                     omega_sys[omega_sys < nyquistfrq], nyquistfrq))
+            omega_complex = np.exp(1j * omega * sys.dt)
         else:
             nyquistfrq = None
+            omega_complex = 1j*omega
 
-        fresp = sys(1j*omega if sys.isctime() else np.exp(1j * omega * sys.dt), squeeze=False)
+        fresp = sys(omega_complex, squeeze=False)
 
         fresp = fresp.transpose((2, 0, 1))
         sigma = np.linalg.svd(fresp, compute_uv=False)
diff --git a/control/tests/freqresp_test.py b/control/tests/freqresp_test.py
@@ -573,12 +573,12 @@ def ss_siso_t():
 
 
 @pytest.fixture
-def tsystem(request, ss_mimo_t, ss_miso_t, ss_simo_t):
+def tsystem(request, ss_mimo_t, ss_miso_t, ss_simo_t, ss_siso_t):
 
     systems = {"ss_mimo": ss_mimo_t,
                "ss_miso": ss_miso_t,
                "ss_simo": ss_simo_t,
-               "ss_siso": ss_simo_t
+               "ss_siso": ss_siso_t
                }
     return systems[request.param]
 
diff --git a/examples/singular-values-plot.ipynb b/examples/singular-values-plot.ipynb
