[Numpy-discussion] Masked arrays: Rationale for "False convention"

[Ondřej Čertík]

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'.

Ondrej