[Numpy-discussion] Questions about C API

Russell E Owen owen at astro.washington.edu
Fri Apr 9 11:49:44 CDT 2004


At 2:32 PM -0400 2004-04-09, Todd Miller wrote:
>On Fri, 2004-04-09 at 13:25, Russell E Owen wrote:
>>  I'm trying to write a median function (surely one is there already,
>>  but if so I've not found it). The fastest technique seems to involve
>>  rearranging the data in place.
>
>You might want to try out numarray.image.median (or
>numarray.image.combine.median for versions < 0.9).

Thanks. Based on the source, it looks like that prefers a stack of 
identical images (instead of a single array, though perhaps one could 
make that case work).

John Hunter also kindly pointed out MLab (which it turns out is 
buried under linear_algebra in numarray: 
numarray.linear_algebra.mlab).

I had been working on a fast median instead of one that sorted the 
whole array, but after timing mlab's median I can probably get away 
with the simple implementation (and skip the C extension).

>>  Also, is there any simple sample code running around for handling
>>  arrays of any type (e.g. with C++ templates)?
>
>I think Peter Verveer did some code like this in the nd_image package.
>The general idea is to constrain the arrays with type tAny in the high
>level API and then switch off of a->descr->type_num to select type
>specific code.

Thank you very much for the explanation of the high level interface 
and the pointer to this sample code.

-- Russell




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