[Numpy-discussion] Medians that ignore values
Fri Sep 19 13:01:13 CDT 2008
Pierre GM wrote:
>> It seems to me that there are pragmatic reasons
>> why people work with NaNs for missing values,
>> that perhaps shd not be dismissed so quickly.
>> But maybe I am overlooking a simple solution.
> nansomething solutions tend to be considerably faster, that might be one
> reason. A lack of visibility of numpy.ma could be a second. In any case, I
> can't but agree with other posters: a NaN in an array usually means something
> went astray.
Additional reasons for using nans:
1) years of experience with Matlab, in which using nan for missing
values is the standard idiom.
2) convenient interfacing with extension code in C or C++.
The latter is a factor in the present use of nan in matplotlib; using
nan for missing values in an array passed into extension code saves
having to pass and process a second (mask) array. It is fast and simple.
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