[python-control-discuss] SF.net SVN: python-control:[111] branches/control-0.4a/src/xferfcn.py

[<kk...@us...>]

Revision: 111
          http://python-control.svn.sourceforge.net/python-control/?rev=111&view=rev
Author:   kkchen
Date:     2011-02-08 22:18:53 +0000 (Tue, 08 Feb 2011)

Log Message:
-----------
Fixes in xferfcn.py

- Division by a scalar now works.
- _common_den() modified so that the numerator coefficient arrays have the same
  size as the common denominator.  This is done by padding with zeros.

Kevin K. Chen <kk...@pr...>

Modified Paths:
--------------
    branches/control-0.4a/src/xferfcn.py

Modified: branches/control-0.4a/src/xferfcn.py
===================================================================
--- branches/control-0.4a/src/xferfcn.py	2011-02-08 22:18:49 UTC (rev 110)
+++ branches/control-0.4a/src/xferfcn.py	2011-02-08 22:18:53 UTC (rev 111)
@@ -344,14 +344,14 @@
     def __div__(self, other):
         """Divide two LTI objects."""
         
+        # Convert the second argument to a transfer function.
+        other = _convertToTransferFunction(other)
+
         if (self.inputs > 1 or self.outputs > 1 or 
             other.inputs > 1 or other.outputs > 1):
             raise NotImplementedError("TransferFunction.__div__ is currently \
 implemented only for SISO systems.")
 
-        # Convert the second argument to a transfer function.
-        other = _convertToTransferFunction(other)
-
         num = polymul(self.num[0][0], other.den[0][0])
         den = polymul(self.den[0][0], other.num[0][0])
         
@@ -487,8 +487,9 @@
         
         computes the single denominator containing all the poles of sys.den, and
         reports it as the array d.  The output numerator array n is modified to
-        use the common denominator.  It is an sys.outputs-by-sys.inputs-by-
-        [something] array.
+        use the common denominator; the coefficient arrays are also padded with
+        zeros to be the same size as d.  n is an sys.outputs-by-sys.inputs-by-
+        len(d) array.
 
         """
         
@@ -588,16 +589,12 @@
                 # Multiply in the missing poles.
                 for p in missingpoles[i][j]:
                     num[i][j] = polymul(num[i][j], [1., -p])
-        # Find the largest numerator polynomial size.
-        largest = 0
+        # Pad all numerator polynomials with zeros so that the numerator arrays
+        # are the same size as the denominator.
         for i in range(self.outputs):
             for j in range(self.inputs):
-                largest = max(largest, len(num[i][j]))
-        # Pad all smaller numerator polynomials with zeros.
-        for i in range(self.outputs):
-            for j in range(self.inputs):
-                num[i][j] = insert(num[i][j], zeros(largest - len(num[i][j])),
-                    zeros(largest - len(num[i][j])))
+                num[i][j] = insert(num[i][j], zeros(len(den) - len(num[i][j])),
+                    zeros(len(den) - len(num[i][j])))
         # Finally, convert the numerator to a 3-D array.
         num = array(num)
         # Remove trivial imaginary parts.  Check for nontrivial imaginary parts.


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