[Numpy-discussion] bug with with fill_values in masked arrays?
Fri Mar 21 11:55:11 CDT 2008
Pierre GM wrote:
> On Wednesday 19 March 2008 19:47:37 Matt Knox wrote:
>>> 1. why am I not getting my NaN's back?
> Because they're gone when you create your masked array.
Really? At least one other post has disagreed with that.
And it does seem odd that a value, even if it's a nan, would be destroyed...
> The idea here is to
> get rid of the nan in your data
No, it's to mask them, otherwise I would have used a normal array, not a ma.
> to avoid potential problems while keeping
> track of where the nans were in the first place.
...like plotting them on a graph, which the current behaviour makes
unworkable, that you end up doing a myarray.filled(0) to get around it,
with imperfect results.
> So, the .data part of your
> masked array should be nan-free,
Why? Surely that should be the source data, of which nan is a valid part?
> and the mask tells you where the nans were.
Right, but why when the masked array is cast back to a list of numbers
if the fill_value of the ma not respected?
>>> 2. why is the wrong fill value being used here?
>> the second element in the array iteration here is actually the
>> numpy.ma.masked constant, which always has the same fill value...
...and that's a bug.
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