docstring updates

murrayrm · murrayrm · commit 598058cb3eb8 · 2021-02-10T21:44:39.000-08:00
diff --git a/control/lti.py b/control/lti.py
@@ -644,8 +644,9 @@ def dcgain(sys):
     Returns
     -------
     gain : ndarray
-        The zero-frequency gain, or np.inf if the system has a pole at the
-        origin, np.nan if there is a pole/zero cancellation at the origin.
+        The zero-frequency gain, or (inf + nanj) if the system has a pole at
+        the origin, (nan + nanj) if there is a pole/zero cancellation at the
+        origin.
 
     """
     return sys.dcgain()
diff --git a/control/statesp.py b/control/statesp.py
@@ -1219,9 +1219,10 @@ def dcgain(self, warn_infinite=False):
         Returns
         -------
         gain : ndarray
-            An array of shape (outputs,inputs); the array will either
-            be the zero-frequency (or DC) gain, or, if the frequency
-            response is singular, the array will be filled with np.inf.
+            An array of shape (outputs,inputs); the array will either be the
+            zero-frequency (or DC) gain, or, if the frequency response is
+            singular, the array will be filled with (inf + nanj).
+
         """
         return self(0, warn_infinite=warn_infinite) if self.isctime() \
             else self(1, warn_infinite=warn_infinite)
diff --git a/control/tests/statesp_test.py b/control/tests/statesp_test.py
@@ -21,7 +21,6 @@
                              rss, ss, tf2ss, _statesp_defaults)
 from control.tests.conftest import ismatarrayout, slycotonly
 from control.xferfcn import TransferFunction, ss2tf
-from control.exception import ControlSlycot
 
 from .conftest import editsdefaults
 
