Ludwig M Brinckmann wrote:

This is a follow-up to an earlier mail that reported a suspected bug in the reduce/minimum operation of numpy.ma <http://numpy.ma>.

I have tried the same code with the scipy sandbox maskedarray implementation and that gives me the correct output. For comparison:

Yes, I think I see where the bug is coming from in numpy.ma; it is assigning fill values for min and max operations as if all integer types were the system default integer. Maskedarray uses a dictionary to assign fill values for these operations, so it correctly takes into account the type. Maskedarray has had much more recent development and maintenance than ma, and may replace it in numpy 1.1. I have not seen any objections to this proposal. From my standpoint, the sooner it happens, the better--unless someone raises a fundamental objection to the approach maskedarray is taking. Eric

# import numpy.core.ma <http://numpy.core.ma> as MA import maskedarray as MA shape = (100) data = numpy.ones(shape, numpy.int16) data[2:40] = 3 data[45:70] = -999 mask = MA.make_mask_none (data.shape) mask[data == -999] = True ma = MA.MaskedArray(data, mask = mask) min = MA.minimum.reduce(ma,0) print min

With maskedarray I get, as expected 1, with numpy.core.ma <http://numpy.core.ma> I get -1, a value that is not in the array.

I am using Python 2.44 on XP, the maskedarray is the svn latest, the numpy.core.ma <http://numpy.core.ma> was 1.0.2, but I have tested it with only the current svn version of ma.py and it produces the wrong output.

Ludwig

On 27/07/07, *Ludwig M Brinckmann* <ludwigbrinckmann@gmail.com <mailto:ludwigbrinckmann@gmail.com>> wrote:

I have ma.minimum.reduce return a minimum value that does not exist in the array.

The following code prints -1 as the minimum of the MA, I believe it should be 1.

import numpy shape = (100) data = numpy.ones (shape, numpy.int16) data[2:40] = 3 # dummy data data[45:70] = -999 # null values mask = numpy.ma.make_mask_none(data.shape) mask[data == -999] = True ma = numpy.ma.MaskedArray(data, mask = mask) min = numpy.ma.minimum.reduce(ma,0) print min

Am I doing something really stupid here?

Ludwig

------------------------------------------------------------------------

_______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion