Replace np.concatenate with np.union1d in statesp._remove_useless_states method

Andrew D. McGuire · Andrew D. McGuire · commit be53eb734dab · 2019-03-25T17:46:15.000-04:00
This ensures that all elements in the array of state indices to be removed are unique.
diff --git a/control/statesp.py b/control/statesp.py
@@ -202,7 +202,7 @@ def _remove_useless_states(self):
         ax0_C = np.where(~self.C.any(axis=0))[1]
         useless_1 = np.intersect1d(ax1_A, ax1_B, assume_unique=True)
         useless_2 = np.intersect1d(ax0_A, ax0_C, assume_unique=True)
-        useless = np.concatenate((useless_1, useless_2))
+        useless = np.union1d(useless_1, useless_2)
 
         # Remove the useless states.
         self.A = delete(self.A, useless, 0)
