added ssdata and tfdata functions

murrayrm · murrayrm · commit 01314a62717b · 2012-10-04T06:05:09.000Z
diff --git a/ChangeLog b/ChangeLog
@@ -1,3 +1,15 @@
+2012-10-03  Richard Murray  <murray@altura.local>
+
+	* tests/matlab_test.py (TestMatlab.testSsdata): unit test
+
+	* src/matlab.py (ssdata, tfdata): new functions to return state
+	space and transfer function object data.  For transfer functions,
+	currenly requires SISO system
+
+	* src/freqplot.py (bode_plot):  Adding np.atleast_1d to the
+	np.squeeze calculations makes it possible to use a single value
+	frequency list (contributed by Benjamin White)
+
 2012-09-09  Richard Murray  <murray@altura.local>
 
 	* tests/statefbk_test.py (TestStatefbk.testAcker): unit test
diff --git a/src/__init__.py b/src/__init__.py
@@ -80,3 +80,4 @@
 from matlab import nichols, rlocus, margin
         # bode and nyquist come directly from freqplot.py
 from matlab import step, impulse, initial, lsim
+from matlab import ssdata, tfdata
diff --git a/src/freqplot.py b/src/freqplot.py
@@ -114,8 +114,8 @@ def bode_plot(syslist, omega=None, dB=False, Hz=False, deg=True,
 
             # Get the magnitude and phase of the system
             mag_tmp, phase_tmp, omega = sys.freqresp(omega)
-            mag = np.squeeze(mag_tmp)
-            phase = np.squeeze(phase_tmp)
+            mag = np.atleast_1d(np.squeeze(mag_tmp))
+            phase = np.atleast_1d(np.squeeze(phase_tmp))
             phase = unwrap(phase)
             if Hz: omega = omega/(2*sp.pi)
             if dB: mag = 20*sp.log10(mag)
diff --git a/src/matlab.py b/src/matlab.py
@@ -1338,3 +1338,45 @@ def lsim(sys, U=0., T=None, X0=0., **keywords):
     T, yout, xout = timeresp.forced_response(sys, T, U, X0,
                                              transpose = True, **keywords)
     return yout, T, xout
+
+# Return state space data as a tuple
+def ssdata(sys):
+    '''
+    Return state space data objects for a system
+    
+    Parameters
+    ----------
+    sys: Lti (StateSpace, or TransferFunction)
+        LTI system whose data will be returned
+
+    Returns
+    -------
+    (A, B, C, D): list of matrices
+        State space data for the system
+    '''
+    ss = _convertToStateSpace(sys)
+    return (ss.A, ss.B, ss.C, ss.D)
+
+# Return transfer function data as a tuple
+def tfdata(sys, **kw):
+    '''
+    Return transfer function data objects for a system
+    
+    Parameters
+    ----------
+    sys: Lti (StateSpace, or TransferFunction)
+        LTI system whose data will be returned
+
+    Keywords
+    --------
+    inputs = int; outputs = int
+        For MIMO transfer function, return num, den for given inputs, outputs
+
+    Returns
+    -------
+    (num, den): numerator and denominator arrays
+        Transfer function coefficients (SISO only)
+    '''
+    tf = _convertToTransferFunction(sys, **kw)
+    
+    return (tf.num, tf.den)
diff --git a/src/xferfcn.py b/src/xferfcn.py
@@ -786,16 +786,16 @@ def _convertToTransferFunction(sys, **kw):
     
     if isinstance(sys, TransferFunction):
         if len(kw):
-            raise TypeError("If sys is a TransferFunction, \
-_convertToTransferFunction cannot take keywords.")
+            raise TypeError("If sys is a TransferFunction, " + 
+                    "_convertToTransferFunction cannot take keywords.")
 
         return sys
     elif isinstance(sys, statesp.StateSpace):
         try:
             from slycot import tb04ad
             if len(kw):
-                raise TypeError("If sys is a StateSpace, \
-                        _convertToTransferFunction cannot take keywords.")
+                raise TypeError("If sys is a StateSpace, " +
+                        "_convertToTransferFunction cannot take keywords.")
 
             # Use Slycot to make the transformation
             # Make sure to convert system matrices to numpy arrays
diff --git a/tests/matlab_test.py b/tests/matlab_test.py
@@ -353,6 +353,32 @@ def testUnwrap(self):
         wrapped = phase % (2 * np.pi)
         unwrapped = unwrap(wrapped)
 
+    def testSISOssdata(self):
+        ssdata_1 = ssdata(self.siso_ss2);
+        ssdata_2 = ssdata(self.siso_tf2);
+        for i in range(len(ssdata_1)):
+            np.testing.assert_array_almost_equal(ssdata_1[i], ssdata_2[i])
+
+    def testMIMOssdata(self):
+        m = (self.mimo_ss1.A, self.mimo_ss1.B, self.mimo_ss1.C, self.mimo_ss1.D)
+        ssdata_1 = ssdata(self.mimo_ss1);
+        for i in range(len(ssdata_1)):
+            np.testing.assert_array_almost_equal(ssdata_1[i], m[i])
+
+    def testSISOtfdata(self):
+        tfdata_1 = tfdata(self.siso_tf2);
+        tfdata_2 = tfdata(self.siso_tf2);
+        for i in range(len(tfdata_1)):
+            np.testing.assert_array_almost_equal(tfdata_1[i], tfdata_2[i])
+
+#! TODO: not yet implemented
+#    def testMIMOtfdata(self):
+#        sisotf = ss2tf(self.siso_ss1)
+#        tfdata_1 = tfdata(sisotf)
+#        tfdata_2 = tfdata(self.mimo_ss1, input=0, output=0)
+#        for i in range(len(tfdata)):
+#            np.testing.assert_array_almost_equal(tfdata_1[i], tfdata_2[i])
+
 def suite():
    return unittest.TestLoader().loadTestsFromTestCase(TestMatlab)
 
