small bugfix to xferfcn._evalfr to correctly give it dt value

sawyerbfuller · bnavigator · commit 5f46b5ba8720 · 2020-12-31T01:14:07.000+01:00
diff --git a/control/xferfcn.py b/control/xferfcn.py
@@ -605,7 +605,7 @@ def _evalfr(self, omega):
         if isdtime(self, strict=True):
             # Convert the frequency to discrete time
             s = exp(1.j * omega * self.dt)
-            if np.any(omega * dt > pi):
+            if np.any(omega * self.dt > pi):
                 warn("_evalfr: frequency evaluation above Nyquist frequency")
         else:
             s = 1.j * omega
