[Scipy-tickets] [SciPy] #651: Bug fixed for scipy.signal.tf2zpk

SciPy scipy-tickets@scipy....
Wed Apr 30 16:41:28 CDT 2008

#651: Bug fixed for scipy.signal.tf2zpk
 Reporter:  bow_der_kleine  |        Owner:  somebody
     Type:  enhancement     |       Status:  new     
 Priority:  normal          |    Milestone:  0.7     
Component:  Other           |      Version:          
 Severity:  normal          |   Resolution:          
 Keywords:                  |  
Comment (by bow_der_kleine):

 For example :

 from scipy.signal import *
 b,a = bessel(20, 0.1)
 z,p,k = tf2zpk(b,a)
 # In this line z == array([], dtype=float64). This is a wrong result.
 b2, a2 = zpk2tf(z,p,k)
 # Here b2 == array([  1.09154777e-17]). It should be the same as b from
 bessel(20, 0.1). But it is not.

 About the code, which you shown from tf2zpk and normalize, I guest, that
 it tries to convert the type of array. But it is not a beautiful code. It
 would be better with something like that.

 a = array(a).astype(float32)
 b = array(b).astype(float32)

Ticket URL: <http://scipy.org/scipy/scipy/ticket/651#comment:2>
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