[python-control-discuss] SF.net SVN: python-control:[154] trunk/src/delay.py

[<bli...@us...>]

Revision: 154
          http://python-control.svn.sourceforge.net/python-control/?rev=154&view=rev
Author:   blinkminster
Date:     2011-04-07 20:12:28 +0000 (Thu, 07 Apr 2011)

Log Message:
-----------
added special case to pade to not crash when given zero time delay

Modified Paths:
--------------
    trunk/src/delay.py

Modified: trunk/src/delay.py
===================================================================
--- trunk/src/delay.py	2011-04-07 20:09:44 UTC (rev 153)
+++ trunk/src/delay.py	2011-04-07 20:12:28 UTC (rev 154)
@@ -54,15 +54,19 @@
     Based on an algorithm in Golub and van Loan, "Matrix Computation" 3rd.
     Ed. pp. 572-574.
     """
-    num = [0. for i in range(n+1)]
-    num[-1] = 1.
-    den = [0. for i in range(n+1)]
-    den[-1] = 1.
-    c = 1.
-    for k in range(1, n+1):
-        c = T * c * (n - k + 1)/(2 * n - k + 1)/k
-        num[n - k] = c * (-1)**k
-        den[n - k] = c 
-    num = [coeff/den[0] for coeff in num]
-    den = [coeff/den[0] for coeff in den]
+    if T == 0:
+        num = [1,]
+        den = [1,]
+    else:
+        num = [0. for i in range(n+1)]
+        num[-1] = 1.
+        den = [0. for i in range(n+1)]
+        den[-1] = 1.
+        c = 1.
+        for k in range(1, n+1):
+            c = T * c * (n - k + 1)/(2 * n - k + 1)/k
+            num[n - k] = c * (-1)**k
+            den[n - k] = c 
+        num = [coeff/den[0] for coeff in num]
+        den = [coeff/den[0] for coeff in den]
     return num, den 


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