[Numpy-discussion] NA masks in the next numpy release?

[Han Genuit]

Yes, to further iterate on that, you can also create multiple masked
views with each its own mask properties. It would be ambiguous to mix
a bit-pattern NA together with standard NA's in the same mask, but you
can make different specialized masked views on the same data.

Also, I like the short and concise abbreviation for 'Not Applicable',
NA. It has more common uses than IGNORE.
(See also here:
http://www.johndcook.com/R_language_for_programmers.html#missing)

Concerning the assignment, it is a bit implicit, I agree, but the
representation and application of masks is also implicit. I think you
only have to know that NA will be a mask assignment and not a data
assignment.