On Mon, Sep 30, 2013 at 9:38 PM, Charles R Harris <charlesr.har...@gmail.com> wrote: > > > > On Mon, Sep 30, 2013 at 7:05 PM, Ondřej Čertík <ondrej.cer...@gmail.com> > wrote: >> >> Hi, >> >> What is the rationale for using False in 'mask' for elements that >> should be included? >> >> http://docs.scipy.org/doc/numpy/reference/maskedarray.generic.html >> >> As opposed to using True for elements that should be included, which >> is what I was intuitively expecting when I started using the masked >> arrays. This "True convention" also happens to be the one used in >> Fortran, see e.g.: >> >> http://gcc.gnu.org/onlinedocs/gfortran/SUM.html >> >> So it's confusing why NumPy would chose a "False convention". Could it >> be, that NumPy views 'mask' as opacity? Then it would make sense to >> use True to make a value 'opaque'. > > > There was a lengthy discussion of this point back when the NA work was done. > You might be able to find the thread with a search. > > As to why it is as it is, I suspect it is historical consistency. Pierre > wrote the masked array package for numpy, but it may very well go back to > the masked array package implemented for Numeric.
I don't know ancient history, but I thought it's "natural". (Actually, I never thought about it.) I always thought `mask` indicates the "masked" (invalid, hidden) values, and masked arrays mask the missing values. http://en.wikipedia.org/wiki/Masking_tape Josef > > Chuck > > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion