Re: [matplotlib-devel] path simplification can decrease the smoothness of data plots

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

I've checked this change into SVN so others can test it out.

Assuming we don't discover any cases where this is clearly inferior, it 
should make it into the next major release.

Mike

Andrew Hawryluk wrote:
>> -----Original Message-----
>> From: Michael Droettboom [mailto:md...@st...]
>> Sent: 16 Jan 2009 1:31 PM
>> To: Andrew Hawryluk
>> Cc: mat...@li...
>> Subject: Re: [matplotlib-devel] path simplification can decrease the
>> smoothness of data plots
>>
>> Michael Droettboom wrote:
>>     
>
> ...
>
>   
>> I've attached a patch that will only include points from the original
>> data in the simplified path.  I hesitate to commit it to SVN, as these
>> things are very hard to get right -- and just because it appears to
>> work better on this data doesn't mean it doesn't create a regression
>>     
> on
>   
>> something else... ;)  That said, it would be nice to confirm that this
>> solution works, because it has the added benefit of being a little
>> simpler computationally.  Be sure to blitz your build directory when
>> testing the patch -- distutils won't pick it up as a dependency.
>>
>> I've attached two PDFs -- one with the original (current trunk)
>> behavior, and one with the new behavior.  I plotted the unsimplified
>> plot in thick blue behind the simplified plot in green, so you can see
>> how much deviation there is between the original data and the
>> simplified line (you'll want to zoom way in with your PDF viewer to
>>     
> see
>   
>> it.)
>>
>> I've also included a new version of your test script which detects
>> "new"
>> data values in the simplified path, and also seeds the random number
>> generator so that results are comparable.  I also set the
>> solid_joinstyle to "round", as it makes the wiggliness less
>>     
> pronounced.
>   
>> (There was another thread on this list recently about making that the
>> default setting).
>>
>> Cheers,
>> Mike
>>
>> --
>> Michael Droettboom
>> Science Software Branch
>> Operations and Engineering Division
>> Space Telescope Science Institute
>> Operated by AURA for NASA
>>     
>
> Thanks for looking into this! The new plot is much improved, and the
> simplified calculations are a pleasant surprise. I was also testing the
> previous algorithm with solid_joinstyle set to "round" as it is the
> default in my matplotlibrc.
>
> I am probably not able to build your patch here, unless building
> matplotlib from source on Windows is easier than I anticipate. May I
> send you some data off the list for you to test?
>
> Regards,
> Andrew
>
> NOVA Chemicals Research & Technology Centre
> Calgary, Canada
>   

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