fixed ticked #6, evalfr does not behave as expected

repagh · repagh · commit 4de4c0e8b9c5 · 2013-05-30T15:50:09.000Z
diff --git a/src/matlab.py b/src/matlab.py
@@ -889,16 +889,20 @@ def zero(sys):
 
     return sys.zero()
 
-def evalfr(sys, omega):
+def evalfr(sys, x):
     """
-    Evaluate the transfer function of an LTI system at an angular frequency.
+    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
 
     Parameters
     ----------
     sys: StateSpace or TransferFunction
         Linear system
-    omega: scalar
-        Frequency 
+    x: scalar
+        Complex number 
 
     Returns
     -------
@@ -917,14 +921,16 @@ def evalfr(sys, omega):
     Examples
     --------
     >>> sys = ss("1. -2; 3. -4", "5.; 7", "6. 8", "9.")
-    >>> evalfr(sys, 1.)
+    >>> evalfr(sys, 1j)
     array([[ 44.8-21.4j]])
     >>> # This is the transfer function matrix evaluated at s = i.
 
     .. todo:: Add example with MIMO system
     """
-
-    return sys.evalfr(omega)
+    if issiso(sys):
+        return sys.horner(x)[0][0]
+    return sys.horner(x)
+        
 
 def freqresp(sys, omega): 
     """
diff --git a/tests/matlab_test.py b/tests/matlab_test.py
@@ -316,13 +316,16 @@ def testFreqresp(self):
         freqresp(self.siso_tf3, w)
 
     def testEvalfr(self):
-        w = 1
-        evalfr(self.siso_ss1, w)
+        w = 1j
+        self.assertEqual(evalfr(self.siso_ss1, w), 44.8-21.4j)
         evalfr(self.siso_ss2, w)
         evalfr(self.siso_ss3, w)
         evalfr(self.siso_tf1, w)
         evalfr(self.siso_tf2, w)
         evalfr(self.siso_tf3, w)
+        np.testing.assert_array_almost_equal(
+            evalfr(self.mimo_ss1, w), 
+            np.array( [[44.8-21.4j, 0.], [0., 44.8-21.4j]]))
 
     def testHsvd(self):
         hsvd(self.siso_ss1)
