[Scipy-svn] r5000 - trunk/scipy/signal

[scipy-svn at scipy.org]

Author: cdavid
Date: 2008-11-06 05:56:24 -0600 (Thu, 06 Nov 2008)
New Revision: 5000

Modified:
   trunk/scipy/signal/filter_design.py
Log:
Mention the warning in tf2zpk and zpk2tf.

Modified: trunk/scipy/signal/filter_design.py
===================================================================
--- trunk/scipy/signal/filter_design.py	2008-11-06 11:55:41 UTC (rev 4999)
+++ trunk/scipy/signal/filter_design.py	2008-11-06 11:56:24 UTC (rev 5000)
@@ -124,6 +124,9 @@
 def tf2zpk(b,a):
     """Return zero, pole, gain (z,p,k) representation from a numerator,
     denominator representation of a linear filter.
+
+    If some values of b are too close to 0, they are removed. In that case, a
+    BadCoefficients warning is emitted.
     """
     b,a = normalize(b,a)
     b = (b+0.0) / a[0]
@@ -146,6 +149,9 @@
     Outputs: (b,a)
 
       b, a --- numerator and denominator polynomials.
+
+    If some values of b are too close to 0, they are removed. In that case, a
+    BadCoefficients warning is emitted.
     """
     z = atleast_1d(z)
     k = atleast_1d(k)
@@ -163,6 +169,9 @@
 
 def normalize(b,a):
     """Normalize polynomial representation of a transfer function.
+
+    If values of b are too close to 0, they are removed. In that case, a
+    BadCoefficients warning is emitted.
     """
     b,a = map(atleast_1d,(b,a))
     if len(a.shape) != 1: