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## Re: [Matplotlib-users] Plot aliasing

 Re: [Matplotlib-users] Plot aliasing From: Kaushik Ghose - 2008-12-28 01:05:47 Hi John, OK. I've managed to pare it down to the following pattern: import pylab N = 1000 x = pylab.zeros(200) x[1] = .5 x[2:24] = 1.0 x[24] = .5 x[26] = -.5 x[27:49] = -1.0 x[49] = -.5 x = pylab.tile(x, 100) pylab.plot(x) The above code is sufficient to repeat the glitch (just resize the window to check this). The half-way values (0.5) are important - if we have a straight jump the glitch isn't visible. I'm sorry but I couldn't find path.py under /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/ so I couldn't try it out. (Is it under a different place in mac?) thanks -Kaushik John Hunter wrote: > On Sat, Dec 27, 2008 at 10:29 AM, Kaushik Ghose > wrote: >> Hi Gang, >> >> I was plotting some data collected from an ADC and noticed an odd aliasing >> issue. Please see the images on the following site. >> >> http://assorted-experience.blogspot.com/2008/12/odd-aliasing-issue-with-matplotlib.html >> >> I wonder if there is any way to avoid this kind of aliasing. I vaguely remember >> our old arch-foe (MATLAB) handles this gracefully. I have found matplotlib's >> plotting to be superior to MATLAB's in every way (except for 3D) and it would be >> nice if aliasing could be handled gracefully. > > I'm almost certain this is a result of the path simplification logic. > Could you upload some sample data and a self contained script so we > can test? > You can test this by editing site-packages/path.py and replacing:: > > self.should_simplify = (len(vertices) >= 128 and > (codes is None or np.all(codes <= Path.LINETO))) > > with:: > > self.should_simplify = False > > Michael, perhaps we could override path.should_simplify with an rc or > line property? > >> Also, thanks for the excellent binary packages for Mac! > > Thanks for testing them!