[Numpy-discussion] Problems with Masked Arrays and NaN values

Nadav Horesh nadavh at VisionSense.com
Tue Nov 4 05:41:09 CST 2003


How's about using the original (unpatched) VTKpython --- I think that
numarray arrays can be casted transparently to Numeric arrays, or you
can explicitly cast them when you call VTKpython functions.

  Nadav.

On Tue, 2003-11-04 at 15:12, Leo Breebaart wrote:
> Nadav Horesh wrote:
> 
> > Look at the numarray package instead of Numeric --- I think it
> > has a better IEEE754 support even without the MA. For most
> > cases, numarray is a 1:1 replacement for Numeric.
> 
> Thanks for the suggestion -- that was just about the one thing I
> hadn't tried yet. I had looked at numarray previously to see
> whether it had improved Masked Arrays, but since it didn't, I
> kinda neglected to look at numarray itself, and you are
> absolutely right: you can print and manipulate arrays containing 
> inf and nan, and logical things will now happen instead of stack
> traces.
> 
> However.
> 
> As I mentioned in my previous message, one of the things I'm
> doing with these arrays is passing them on to the VTK Python
> wrappers for use in visualisation functions. These VTK wrappers
> are based on Numeric, nor numarray, so I had to manually patch
> them to make them work with numarray as well.
> 
> So far so, good, but there was one problem: at one point, calls
> are made to an internal VTK function, using 'a.flat' as an input
> parameter (where 'a' is now a numarray array instead of a Numeric
> one.)
> 
> This call fails, because in Numeric the type of 'a.flat' is
> '<type array>', whereas in numarray the type is '<class
> 'numarray.numarraycode.Numarray>'.
> 
> I managed to solve this by feeding the function in question
> a.flat._data (<type 'Memory'>) instead, but I am wondering if
> this is really the best solution, or if there's perhaps some
> other (more portable? more reliable?) way of handing off a
> numarray's internal data to an external function.
> 
> Once again, all feedback will be most welcome...





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