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

sawyerbfuller · sawyerbfuller · commit 7a9bcd405c70 · 2020-07-17T19:16:18.000-07:00
diff --git a/control/xferfcn.py b/control/xferfcn.py
@@ -604,7 +604,7 @@ 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
