python-control · murrayrm · Jan 19, 2021 · Jan 16, 2021 · Jan 17, 2021 · Jan 17, 2021
diff --git a/control/config.py b/control/config.py
@@ -16,7 +16,10 @@
 # Package level default values
 _control_defaults = {
     'control.default_dt': 0,
-    'control.squeeze_frequency_response': None
+    'control.squeeze_frequency_response': None,
+    'control.squeeze_time_response': True,
+    'control.squeeze_time_response': None,
+    'forced_response.return_x': False,
 }
 defaults = dict(_control_defaults)
 
@@ -211,6 +214,7 @@ def use_legacy_defaults(version):
     #
     # Go backwards through releases and reset defaults
     #
+    reset_defaults()            # start from a clean slate
 
     # Version 0.9.0:
     if major == 0 and minor < 9:
@@ -230,4 +234,10 @@ def use_legacy_defaults(version):
         # turned off _remove_useless_states
         set_defaults('statesp', remove_useless_states=True)
 
+        # forced_response no longer returns x by default
+        set_defaults('forced_response', return_x=True)
+
+        # time responses are only squeezed if SISO
+        set_defaults('control', squeeze_time_response=True)
+
     return (major, minor, patch)
diff --git a/control/iosys.py b/control/iosys.py
@@ -37,7 +37,7 @@
 from warnings import warn
 
 from .statesp import StateSpace, tf2ss
-from .timeresp import _check_convert_array
+from .timeresp import _check_convert_array, _process_time_response
 from .lti import isctime, isdtime, common_timebase
 from . import config
 
@@ -450,6 +450,10 @@ def find_state(self, name):
         """Find the index for a state given its name (`None` if not found)"""
         return self.state_index.get(name, None)
 
+    def issiso(self):
+        """Check to see if a system is single input, single output"""
+        return self.ninputs == 1 and self.noutputs == 1
+
     def feedback(self, other=1, sign=-1, params={}):
         """Feedback interconnection between two input/output systems
 
@@ -1353,7 +1357,7 @@ def __init__(self, io_sys, ss_sys=None):
 
 
 def input_output_response(sys, T, U=0., X0=0, params={}, method='RK45',
-                          return_x=False, squeeze=True):
+                          transpose=False, return_x=False, squeeze=None):
 
     """Compute the output response of a system to a given input.
 
@@ -1373,18 +1377,22 @@ def input_output_response(sys, T, U=0., X0=0, params={}, method='RK45',
     return_x : bool, optional
         If True, return the values of the state at each time (default = False).
     squeeze : bool, optional
-        If True (default), squeeze unused dimensions out of the output
-        response.  In particular, for a single output system, return a
-        vector of shape (nsteps) instead of (nsteps, 1).
+        If True and if the system has a single output, return the system
+        output as a 1D array rather than a 2D array.  If False, return the
+        system output as a 2D array even if the system is SISO.  Default value
+        set by config.defaults['control.squeeze_time_response'].
 
     Returns
     -------
     T : array
         Time values of the output.
     yout : array
-        Response of the system.
+        Response of the system.  If the system is SISO and squeeze is not
+        True, the array is 1D (indexed by time).  If the system is not SISO or
+        squeeze is False, the array is 2D (indexed by the output number and
+        time).
     xout : array
-        Time evolution of the state vector (if return_x=True)
+        Time evolution of the state vector (if return_x=True).
 
     Raises
     ------
@@ -1420,12 +1428,8 @@ def input_output_response(sys, T, U=0., X0=0, params={}, method='RK45',
         for i in range(len(T)):
             u = U[i] if len(U.shape) == 1 else U[:, i]
             y[:, i] = sys._out(T[i], [], u)
-        if squeeze:
-            y = np.squeeze(y)
-        if return_x:
-            return T, y, []
-        else:
-            return T, y
+        return _process_time_response(sys, T, y, [], transpose=transpose,
+                                      return_x=return_x, squeeze=squeeze)
 
     # create X0 if not given, test if X0 has correct shape
     X0 = _check_convert_array(X0, [(nstates,), (nstates, 1)],
@@ -1500,14 +1504,8 @@ def ivp_rhs(t, x): return sys._rhs(t, x, u(t))
     else:                       # Neither ctime or dtime??
         raise TypeError("Can't determine system type")
 
-    # Get rid of extra dimensions in the output, of desired
-    if squeeze:
-        y = np.squeeze(y)
-
-    if return_x:
-        return soln.t, y, soln.y
-    else:
-        return soln.t, y
+    return _process_time_response(sys, soln.t, y, soln.y, transpose=transpose,
+                                  return_x=return_x, squeeze=squeeze)
 
 
 def find_eqpt(sys, x0, u0=[], y0=None, t=0, params={},

diff --git a/control/matlab/timeresp.py b/control/matlab/timeresp.py
@@ -59,15 +59,13 @@ def step(sys, T=None, X0=0., input=0, output=None, return_x=False):
     '''
     from ..timeresp import step_response
 
-    T, yout, xout = step_response(sys, T, X0, input, output,
-                                  transpose=True, return_x=True)
+    # Switch output argument order and transpose outputs
+    out = step_response(sys, T, X0, input, output,
+                        transpose=True, return_x=return_x)
+    return (out[1], out[0], out[2]) if return_x else (out[1], out[0])
 
-    if return_x:
-        return yout, T, xout
-
-    return yout, T
-
-def stepinfo(sys, T=None, SettlingTimeThreshold=0.02, RiseTimeLimits=(0.1, 0.9)):
+def stepinfo(sys, T=None, SettlingTimeThreshold=0.02,
+             RiseTimeLimits=(0.1, 0.9)):
     '''
     Step response characteristics (Rise time, Settling Time, Peak and others).
 
@@ -110,6 +108,7 @@ def stepinfo(sys, T=None, SettlingTimeThreshold=0.02, RiseTimeLimits=(0.1, 0.9))
     '''
     from ..timeresp import step_info
 
+    # Call step_info with MATLAB defaults
     S = step_info(sys, T, None, SettlingTimeThreshold, RiseTimeLimits)
 
     return S
@@ -164,13 +163,11 @@ def impulse(sys, T=None, X0=0., input=0, output=None, return_x=False):
     >>> yout, T = impulse(sys, T)
     '''
     from ..timeresp import impulse_response
-    T, yout, xout = impulse_response(sys, T, X0, input, output,
-                                     transpose = True, return_x=True)
-
-    if return_x:
-        return yout, T, xout
 
-    return yout, T
+    # Switch output argument order and transpose outputs
+    out = impulse_response(sys, T, X0, input, output,
+                           transpose = True, return_x=return_x)
+    return (out[1], out[0], out[2]) if return_x else (out[1], out[0])
 
 def initial(sys, T=None, X0=0., input=None, output=None, return_x=False):
     '''
@@ -222,13 +219,12 @@ def initial(sys, T=None, X0=0., input=None, output=None, return_x=False):
 
     '''
     from ..timeresp import initial_response
+
+    # Switch output argument order and transpose outputs
     T, yout, xout = initial_response(sys, T, X0, output=output,
                                      transpose=True, return_x=True)
+    return (yout, T, xout) if return_x else (yout, T)
 
-    if return_x:
-        return yout, T, xout
-
-    return yout, T
 
 def lsim(sys, U=0., T=None, X0=0.):
     '''
@@ -273,5 +269,7 @@ def lsim(sys, U=0., T=None, X0=0.):
     >>> yout, T, xout = lsim(sys, U, T, X0)
     '''
     from ..timeresp import forced_response
-    T, yout, xout = forced_response(sys, T, U, X0, transpose = True)
-    return yout, T, xout
+
+    # Switch output argument order and transpose outputs (and always return x)
+    out = forced_response(sys, T, U, X0, return_x=True, transpose=True)
+    return out[1], out[0], out[2]
diff --git a/control/tests/config_test.py b/control/tests/config_test.py
@@ -211,12 +211,15 @@ def test_legacy_defaults(self):
             ct.use_legacy_defaults('0.8.3')
             assert(isinstance(ct.ss(0, 0, 0, 1).D, np.matrix))
         ct.reset_defaults()
-        assert(isinstance(ct.ss(0, 0, 0, 1).D, np.ndarray))
-        assert(not isinstance(ct.ss(0, 0, 0, 1).D, np.matrix))
+        assert isinstance(ct.ss(0, 0, 0, 1).D, np.ndarray)
+        assert not isinstance(ct.ss(0, 0, 0, 1).D, np.matrix)
+
+        ct.use_legacy_defaults('0.8.4')
+        assert ct.config.defaults['forced_response.return_x'] is True
 
         ct.use_legacy_defaults('0.9.0')
-        assert(isinstance(ct.ss(0, 0, 0, 1).D, np.ndarray))
-        assert(not isinstance(ct.ss(0, 0, 0, 1).D, np.matrix))
+        assert isinstance(ct.ss(0, 0, 0, 1).D, np.ndarray)
+        assert not isinstance(ct.ss(0, 0, 0, 1).D, np.matrix)
 
         # test that old versions don't raise a problem
         ct.use_legacy_defaults('REL-0.1')

diff --git a/control/tests/discrete_test.py b/control/tests/discrete_test.py
@@ -353,9 +353,11 @@ def testSimulation(self, tsys):
         tout, yout = step_response(tsys.siso_ss1d, T)
         tout, yout = impulse_response(tsys.siso_ss1d)
         tout, yout = impulse_response(tsys.siso_ss1d, T)
-        tout, yout, xout = forced_response(tsys.siso_ss1d, T, U, 0)
-        tout, yout, xout = forced_response(tsys.siso_ss2d, T, U, 0)
-        tout, yout, xout = forced_response(tsys.siso_ss3d, T, U, 0)
+        tout, yout = forced_response(tsys.siso_ss1d, T, U, 0)
+        tout, yout = forced_response(tsys.siso_ss2d, T, U, 0)
+        tout, yout = forced_response(tsys.siso_ss3d, T, U, 0)
+        tout, yout, xout = forced_response(tsys.siso_ss1d, T, U, 0,
+                                           return_x=True)
 
     def test_sample_system(self, tsys):
         # Make sure we can convert various types of systems

diff --git a/control/tests/flatsys_test.py b/control/tests/flatsys_test.py
@@ -48,7 +48,7 @@ def test_double_integrator(self, xf, uf, Tf):
         T = np.linspace(0, Tf, 100)
         xd, ud = traj.eval(T)
 
-        t, y, x = ct.forced_response(sys, T, ud, x1)
+        t, y, x = ct.forced_response(sys, T, ud, x1, return_x=True)
         np.testing.assert_array_almost_equal(x, xd, decimal=3)
 
     def test_kinematic_car(self):