sampling a LinearIOSystem returns a LinearIOSystem

murrayrm · murrayrm · commit 2fcc287b34c6 · 2023-03-18T10:33:23.000-07:00
diff --git a/control/iosys.py b/control/iosys.py
@@ -676,6 +676,12 @@ def __init__(self, linsys, **kwargs):
         StateSpace.__init__(
             self, linsys, remove_useless_states=False, init_namedio=False)
 
+    # When sampling a LinearIO system, return a LinearIOSystem
+    def sample(self, *args, **kwargs):
+        return LinearIOSystem(StateSpace.sample(self, *args, **kwargs))
+
+    sample.__doc__ = StateSpace.sample.__doc__
+
     # The following text needs to be replicated from StateSpace in order for
     # this entry to show up properly in sphinx doccumentation (not sure why,
     # but it was the only way to get it to work).
diff --git a/control/tests/iosys_test.py b/control/tests/iosys_test.py
@@ -2036,3 +2036,14 @@ def test_find_eqpt(x0, ix, u0, iu, y0, iy, dx0, idx, dt, x_expect, u_expect):
     # Check that we got the expected result as well
     np.testing.assert_allclose(np.array(xeq), x_expect, atol=1e-6)
     np.testing.assert_allclose(np.array(ueq), u_expect, atol=1e-6)
+
+def test_iosys_sample():
+    csys = ct.rss(2, 1, 1)
+    dsys = csys.sample(0.1)
+    assert isinstance(dsys, ct.LinearIOSystem)
+    assert dsys.dt == 0.1
+
+    csys = ct.rss(2, 1, 1)
+    dsys = ct.sample_system(csys, 0.1)
+    assert isinstance(dsys, ct.LinearIOSystem)
+    assert dsys.dt == 0.1
diff --git a/control/tests/kwargs_test.py b/control/tests/kwargs_test.py
@@ -86,8 +86,8 @@ def test_kwarg_search(module, prefix):
      (control.lqr, 1, 0, ([[1, 0], [0, 1]], [[1]]), {}),
      (control.linearize, 1, 0, (0, 0), {}),
      (control.pzmap, 1, 0, (), {}),
-     (control.rlocus, 0, 1, ( ), {}),
-     (control.root_locus, 0, 1, ( ), {}),
+     (control.rlocus, 0, 1, (), {}),
+     (control.root_locus, 0, 1, (), {}),
      (control.rss, 0, 0, (2, 1, 1), {}),
      (control.set_defaults, 0, 0, ('control',), {'default_dt': True}),
      (control.ss, 0, 0, (0, 0, 0, 0), {'dt': 1}),
@@ -101,7 +101,9 @@ def test_kwarg_search(module, prefix):
      (control.InputOutputSystem, 0, 0, (),
       {'inputs': 1, 'outputs': 1, 'states': 1}),
      (control.InputOutputSystem.linearize, 1, 0, (0, 0), {}),
-     (control.StateSpace, 0, 0, ([[-1, 0], [0, -1]], [[1], [1]], [[1, 1]], 0), {}),
+     (control.LinearIOSystem.sample, 1, 0, (0.1,), {}),
+     (control.StateSpace, 0, 0,
+      ([[-1, 0], [0, -1]], [[1], [1]], [[1, 1]], 0), {}),
      (control.TransferFunction, 0, 0, ([1], [1, 1]), {})]
 )
 def test_unrecognized_kwargs(function, nsssys, ntfsys, moreargs, kwargs,
@@ -202,6 +204,7 @@ def test_matplotlib_kwargs(function, nsysargs, moreargs, kwargs, mplcleanup):
         interconnect_test.test_interconnect_exceptions,
     'LinearIOSystem.__init__':
         interconnect_test.test_interconnect_exceptions,
+    'LinearIOSystem.sample': test_unrecognized_kwargs,
     'NonlinearIOSystem.__init__':
         interconnect_test.test_interconnect_exceptions,
     'StateSpace.__init__': test_unrecognized_kwargs,
