[Scipy-tickets] [SciPy] #1850: scipy.signal.bode() function does not plote phase shifts larger +- 180° correctly

SciPy Trac scipy-tickets@scipy....
Thu Feb 21 12:02:46 CST 2013


#1850: scipy.signal.bode() function does not plote phase shifts larger +- 180°
correctly
--------------------------+-------------------------------------------------
 Reporter:  Niklas        |       Owner:  cdavid
     Type:  enhancement   |      Status:  new   
 Priority:  normal        |   Milestone:  0.12.0
Component:  scipy.signal  |     Version:  0.11.0
 Keywords:  bode          |  
--------------------------+-------------------------------------------------
 When using the scipy.signal.bode function to create a bode plot, you run
 into problems when trying to plot the phase of systems which a phase shift
 larger than +-180°.[[BR]]

 When the phase shift reaches -180° it does not go on to -181° but instead
 jumps to +179°. I will append a Picture as an example.

 Code which I used to create the example:

 {{{
 from scipy import signal
 from pylab import *

 sys = signal.lti([6],[0,-1,-20,-20],[1])
 w,mag,phi = sys.bode()
 subplot(211)
 semilogx(w,mag)
 subplot(212)
 semilogx(w,phi)
 show()
 }}}

 Example output image:[[BR]]

 [https://dl.dropbox.com/u/15426632/bode.png]

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1850>
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