move warning to before conversion

control/timeresp.py

@@ -302,6 +302,13 @@ def forced_response(sys, T=None, U=0., X0=0., transpose=False,
             "return_x specified for a transfer function system. Internal "
             "conversion to state space used; results may meaningless.")
 
+    # If we are passed a transfer function and X0 is non-zero, warn the user
+    if isinstance(sys, TransferFunction) and np.any(X0 != 0):
+        warnings.warn(
+            "Non-zero initial condition given for transfer function system. "
+            "Internal conversion to state space used; may not be consistent "
+            "with given X0.")
+
     sys = _convert_to_statespace(sys)
     A, B, C, D = np.asarray(sys.A), np.asarray(sys.B), np.asarray(sys.C), \
         np.asarray(sys.D)
@@ -358,12 +365,6 @@ def forced_response(sys, T=None, U=0., X0=0., transpose=False,
     X0 = _check_convert_array(X0, [(n_states,), (n_states, 1)],
                               'Parameter ``X0``: ', squeeze=True)
 
-    # If we are passed a transfer function and X0 is non-zero, warn the user
-    if isinstance(sys, TransferFunction) and np.any(X0 != 0):
-        warnings.warn(
-            "Non-zero initial condition given for transfer function system. "
-            "Internal conversion to state space used; may not be consistent "
-            "with given X0.")
 
     xout = np.zeros((n_states, n_steps))
     xout[:, 0] = X0