[Numpy-discussion] MA bug or feature? (original) (raw)

Pierre GM pgmdevlist at mailcan.com
Thu Jun 22 15:15:15 EDT 2006

On Wednesday 21 June 2006 22:01, Michael Sorich wrote:

I was setting the fillvalue as 'NA' when constructing the array so the masked values would be printed as 'NA'. It is not a big deal to avoid doing this.

You can use masked_print_option, as illustrated below, without using a fill_value incompatible with your data type.

import numpy.core.ma as MA X = MA.array([1,2,3],maks=[0,1,0]) print X [1 -- 3] MA.maskedprintoption=MA.MaskedPrintOption('N/A') print X [1 N/A 3]

Nevertheless, the differences between a masked array with a boolean mask and a mask of booleans have caused me trouble before. Especially when there are hidden in-place conversions of a mask which is a array of False to a mask which is False. e.g.

OK, I'm still using 0.9.8 and I can't help you with this one. In that version,
N.asarray transforms the MA into a ndarray, so you lose the mask.

But I wonder: if none of your values are masked, the natural behavior would be to have data.mask==nomask, which speeds up things a bit. This gain of time is why I was suggesting that mask would be forced to nomask at the creation, if mask.any()==False.

Could you give me some examples of cases where you need the mask to stay as an array of False ? If you need to access the mask as an array, you can always use MA.getmaskarray.

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