Mailman 3 June 2016 - SciPy-User

that's so gooood
by jaonary＠free.fr 12 Jun '16

12 Jun '16

Just take a look at this stuff, it's reaaly good, more info here <http://fondezulty.antientitlement.com/aerocs> Regards, jaonary(a)free.fr

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*** SPAM *** last news
by Samuel Thibault 12 Jun '16

12 Jun '16

Hi, Here are some news since we've met last time, just read'em here <http://cithongisi.votejimmy.org/aefzswwg> Samuel Thibault

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KS 2-sample p-value
by Moy 11 Jun '16

11 Jun '16

Hi folks. I'm curious about the p-value computation for the 2-sample KS test (lines 4298-4302 here [1], link below). Can someone please give me a reference for this, in particular for the mysterious "en + 0.12 + 0.11 / en" piece? I've looked at the MIT OpenCourseWare notes on KS [2] and at the SciPy docs for kstwobign but I'm still totally confuzzled by that piece. Thanks for your time! Moy 1: https://github.com/scipy/scipy/blob/master/scipy/stats/stats.py#L4298 2: http://ocw.mit.edu/courses/mathematics/18-443-statistics-for-applications-f…

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problem with signal.group_delay
by Neal Becker 07 Jun '16

07 Jun '16

Here is my test code (opt.loop_bw = 100e3, sps=2) from scipy import signal bw = opt.loop_bw/(sps*250e6) sos = signal.ellip (8, 0.5, 80, 0.5 * bw, output='sos') bas = [signal.sos2tf(s[np.newaxis,:]) for s in sos] ## my group delay code from group_delay import group_delay2 << my group_delay code delays = [group_delay2 (ba[0], ba[1])[0] for ba in bas] ## scipy group delay code delays2 = [signal.group_delay ((ba[0], ba[1]), w=1e-3) for ba in bas] ## print ('delays:', delays) print ('delay:', sum(delays)) delay = sum(delays) scipy group delay code gives me: /home/nbecker/anaconda3/envs/py35/lib/python3.5/site- packages/scipy/signal/filter_design.py:343: UserWarning: The group delay is singular at frequencies [0.001], setting to 0 format(", ".join("{0:.3f}".format(ws) for ws in w[singular])) I have my own group delay code, that I wrote based on https://ccrma.stanford.edu/~jos/fp/Numerical_Computation_Group_Delay.html This seems to give a correct result. My code is attached. It is using my own wrapper for fftw for fft, but of course you can use whatever you like. ,----[ /home/nbecker/sigproc/group_delay.py ] | ## delay = real[dft(n*h(n))/dft(h(n))] | '''https://ccrma-www.stanford.edu/~jos/filters/Numerical_Computation_Group_Del…''' | | import numpy as np | from numpy_fncs import rotate | | def group_delay (a, fftsize=256): | from fft3 import fft, FORWARD | the_fft = fft (fftsize, FORWARD) | if (len(a) < the_fft.size): | padded = np.concatenate ((a, np.zeros (the_fft.size-len(a), | dtype=complex))) | else: | padded = a | ## num = rotate (the_fft (np.arange (the_fft.size) * padded), | ## the_fft.size/2) den = rotate (the_fft (padded), the_fft.size/2) | num = the_fft (np.arange (the_fft.size) * padded) | den = the_fft (padded) | poles = abs (den) < 1e-50 | num[poles] = 0 | den[poles] = 1 | delay = (num / den).real | return delay | | def group_delay2 (a, b, fftsize=256): | c = np.convolve (a, np.conjugate (b)[::-1]) | return group_delay (c) - len (b) | | if __name__ == "__main__": | ## a = np.array ((0,0,1,0,0),dtype=complex) | ## d = group_delay (a) | ## print d | ## b = np.array ((1,0),dtype=complex) | ## print group_delay2 (a, b) | from scipy.signal import butter | a,b = butter (7, .4) | ##a,b = ((0,1), (1,)) | d = group_delay2 (a, b) | from pylab import plot, show | plot (np.linspace (0, 1, len(d)), d) | show() | `----

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EuroSciPy 2016
by Pierre de Buyl 07 Jun '16

07 Jun '16

Dear NumPy and SciPy communities, No annoucement was made here for EuroSciPy 2016 I believe. The call for contributions (talks, posters, sprints) is still open for a few days. EuroSciPy 2016 takes place in Erlangen, Germany, from the 23 to the 27 of August and consists of two days of tutorials (beginner and advanced tracks) and two days of conference representing many fields of science, with a focus on Python tools for science. A day of sprints follows (sprints TBA). The keynote speakers are Gaël Varoquaux and Abby Cabunoc Mayes and we can expect a rich tutorial and scientific program! Videos from previous years are available at https://www.youtube.com/playlist?list=PLYx7XA2nY5GeQCCugyvtnHMVLdhYlrRxH and https://www.youtube.com/playlist?list=PLYx7XA2nY5Gcpabmu61kKcToLz0FapmHu Visit us, register and submit an abstract on our website! https://www.euroscipy.org/2016/ SciPythonic regards, The EuroSciPy 2016 team

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filtfilt for sos?
by Neal Becker 07 Jun '16

07 Jun '16

I'm wondering about applying filtfilt to sos sections. Would it be reasonable to simply apply filtfilt to each 2nd order section, feeding the output of the 1st into the 2nd? My guess is that isn't correct, and that filtfilt needs to be modified to accept a cascaded filter (instead of a single filter section specified by a,b).

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plot sos (freqz for sos) filter
by Neal Becker 06 Jun '16

06 Jun '16

Happy to see sos format supported. Getting the response of the sos design requires a little effort. A nice addition would be for freqz to directly support an sos input. Here's some code which I'm using for now: sos = signal.ellip (8, 0.5, 80, 0.5 * 500e3/(sps*250e6), output='sos') ba = [signal.sos2tf(s[np.newaxis,:]) for s in sos] ws = np.pi * np.logspace (-4, 0, num=500) wh = [signal.freqz (_[0],_[1],worN=ws) for _ in ba] plt.semilogx (wh[0][0]/np.pi, np.clip (20*np.log10(np.abs(np.prod ([_[1] for _ in wh], axis=0))),-100,0))

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