Re: [Matplotlib-users] Unexpected beaviour when plotting narrow "peaks"

[Michael D. <md...@st...>]

I have fixed this bug that was causing peaks to be truncated in SVN 
r7895 and r7896.  It should make it into the next bugfix release.

Mike

Michael Droettboom wrote:
> It looks like the path simplification code is failing on this.  As a 
> workaround, you can turn it off:
>
>   rcParams['path.simplify'] = False
>
> or reduce the threshold below which vertices are removed:
>
>   rcParams['path.simplify_threshold'] = 0.0001
>
> In the meantime, I'll look further into why this is failing.  Perhaps we 
> need a lower default threshold.
>
> Mike
>
> Henrik Wallin wrote:
>   
>> Hello all,
>>
>> I'm sorry if this has been treated before, but I haven't found
>> anything when searching the archives or the net.
>>
>> Basically, the problem surfaces when plotting FFT spectras using many
>> data points. The amplitudes of the peaks in the spectra then seem to
>> depend on the size of the plot window.
>>
>> Example code:
>>
>>
>>   
>>     
>>>>> from pylab import *
>>>>> t=arange(65536)
>>>>> plot(abs(fft(sin(2*pi*.01*t)*blackman(len(t)))))
>>>>>         
>>>>>           
>> [<matplotlib.lines.Line2D object at 0x03871990>]
>>   
>>     
>>>>> show()
>>>>>         
>>>>>           
>> With the original window size (WXAgg backend), I get maximum peaks at
>> about 390. Zooming in on the peak will increase the amplitude.
>> Resizing the window can also make the amplitude increase.
>>
>> The expected amplitude is:
>>
>>   
>>     
>>>>> max(abs(fft(sin(2*pi*.01*t)*blackman(len(t)))))
>>>>>         
>>>>>           
>> 12891.96683092583
>>
>> Is this a known problem, or should I file a bug report? Is there any
>> workaround (except decreasing the length of t, and thus the level of
>> detail)?
>>
>> I'm using ActivePython 2.6.3.7 for windows, matplotlib 0.99.1 binary,
>> numpy 1.3.0 and wxPython-unicode-2.8.10.1. I've also tried with the
>> TkAgg backend, which gives similar results.
>>
>> Thanks,
>> Henrik
>>
>> ------------------------------------------------------------------------------
>> Come build with us! The BlackBerry(R) Developer Conference in SF, CA
>> is the only developer event you need to attend this year. Jumpstart your
>> developing skills, take BlackBerry mobile applications to market and stay 
>> ahead of the curve. Join us from November 9 - 12, 2009. Register now!
>> http://p.sf.net/sfu/devconference
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>>   
>>     
>
>   

-- 
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA