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
> <kaushik_gh...@hms.harvard.edu> 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!

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