lti.evalfr now wraps sys._evalfr rather than sys.horner

sawyerbfuller · sawyerbfuller · commit 8e3ddd2e00b9 · 2020-07-23T02:29:13.000-07:00
diff --git a/control/lti.py b/control/lti.py
@@ -379,20 +379,16 @@ def damp(sys, doprint=True):
                       (p.real, p.imag, d, w))
     return wn, damping, poles
 
-def evalfr(sys, x):
+def evalfr(sys, omega):
     """
-    Evaluate the transfer function of an LTI system for a single complex
-    number x.
-
-    To evaluate at a frequency, enter x = omega*j, where omega is the
-    frequency in radians
+    Evaluate the transfer function of an LTI system at a frequency omega.
 
     Parameters
     ----------
     sys: StateSpace or TransferFunction
         Linear system
-    x: scalar
-        Complex number
+    omega: scalar
+        frequency in rad/sec
 
     Returns
     -------
@@ -405,22 +401,19 @@ def evalfr(sys, x):
 
     Notes
     -----
-    This function is a wrapper for StateSpace.evalfr and
-    TransferFunction.evalfr.
+    This function is a wrapper for StateSpace._evalfr and
+    TransferFunction._evalfr.
 
     Examples
     --------
     >>> sys = ss("1. -2; 3. -4", "5.; 7", "6. 8", "9.")
-    >>> evalfr(sys, 1j)
+    >>> evalfr(sys, 1)
     array([[ 44.8-21.4j]])
-    >>> # This is the transfer function matrix evaluated at s = i.
+    >>> # This is the transfer function matrix evaluated at s = 1.
 
     .. todo:: Add example with MIMO system
     """
-    if issiso(sys):
-        return sys.horner(x)[0][0]
-    return sys.horner(x)
-
+    return sys._evalfr(omega)
 
 def freqresp(sys, omega):
     """
diff --git a/control/tests/matlab_test.py b/control/tests/matlab_test.py
@@ -369,7 +369,7 @@ def testFreqresp(self):
         freqresp(self.siso_tf3, w)
 
     def testEvalfr(self):
-        w = 1j
+        w = 1
         np.testing.assert_almost_equal(evalfr(self.siso_ss1, w), 44.8-21.4j)
         evalfr(self.siso_ss2, w)
         evalfr(self.siso_ss3, w)
diff --git a/control/tests/statesp_array_test.py b/control/tests/statesp_array_test.py
@@ -195,7 +195,7 @@ def test_evalfr(self):
                  0.128919037199125 - 0.143824945295405j]]
 
         # Correct versions of the call
-        np.testing.assert_almost_equal(evalfr(sys, 1j), resp)
+        np.testing.assert_almost_equal(evalfr(sys, 1), resp)
         np.testing.assert_almost_equal(sys._evalfr(1.), resp)
 
         # Deprecated version of the call (should generate warning)
diff --git a/control/tests/statesp_test.py b/control/tests/statesp_test.py
@@ -204,7 +204,7 @@ def test_evalfr(self):
                  0.128919037199125 - 0.143824945295405j]]
 
         # Correct versions of the call
-        np.testing.assert_almost_equal(evalfr(sys, 1j), resp)
+        np.testing.assert_almost_equal(evalfr(sys, 1), resp)
         np.testing.assert_almost_equal(sys._evalfr(1.), resp)
 
         # Deprecated version of the call (should generate warning)
@@ -668,8 +668,8 @@ def test_sample_system_prewarping(self):
         plant = StateSpace(A,B,C,0)
         plant_d_warped = plant.sample(Ts, 'bilinear', prewarp_frequency=wwarp)
         np.testing.assert_array_almost_equal(
-            evalfr(plant, wwarp*1j), 
-            evalfr(plant_d_warped, np.exp(wwarp*1j*Ts)), 
+            evalfr(plant, wwarp), 
+            evalfr(plant_d_warped, wwarp), 
             decimal=4)
 
 
diff --git a/control/tests/xferfcn_test.py b/control/tests/xferfcn_test.py
@@ -391,10 +391,10 @@ def test_evalfr_siso(self):
 
         sys = TransferFunction([1., 3., 5], [1., 6., 2., -1])
 
-        np.testing.assert_array_almost_equal(evalfr(sys, 1j),
+        np.testing.assert_array_almost_equal(evalfr(sys, 1),
                                              np.array([[-0.5 - 0.5j]]))
         np.testing.assert_array_almost_equal(
-            evalfr(sys, 32j),
+            evalfr(sys, 32),
             np.array([[0.00281959302585077 - 0.030628473607392j]]))
 
         # Test call version as well
@@ -929,8 +929,8 @@ def test_sample_system_prewarping(self):
         plant = ss2tf(plant)
         plant_d_warped = plant.sample(Ts, 'bilinear', prewarp_frequency=wwarp)
         np.testing.assert_array_almost_equal(
-            evalfr(plant, wwarp*1j), 
-            evalfr(plant_d_warped, np.exp(wwarp*1j*Ts)), 
+            evalfr(plant, wwarp), 
+            evalfr(plant_d_warped, wwarp), 
             decimal=4)
 
 
