[Numpy-discussion] Medians that ignore values
Pierre GM
pgmdevlist@gmail....
Thu Sep 18 11:48:51 CDT 2008
On Thursday 18 September 2008 10:59:12 Peter Saffrey wrote:
> I had looked at masked arrays, but couldn't quite get them to work.
That's unfortunate.
> >>> from numeric import *
Mmh, typo?
> >>> from pylab import rand
> >>> a = rand(10,3)
> >>> a[a > 0.8] = nan
> >>> m = ma.masked_array(a, isnan(a))
> >>> m
Another way would be m = ma.masked_where(a>0.8,a)
> Remember I want medians of each triple, so I need to median the
> transposed matrix:
> >>> median(m.T)
Ohoh. What version of numpy are you using ? if you don't give an axis
parameter, you should get the median of the flattened array, therefore a
scalar, not an array.
Anyway: you should use ma.median for masked arrays. Else, you're just keeping
the NaNs where they were.
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