[Numpy-discussion] use for missing (ignored) data?

[Neal Becker]

I'm wondering what is the use for the ignored data feature?

I can use:

A[valid_A_indexes] = whatever

to process only the 'non-ignored' portions of A.  So at least some simple cases 
of ignored data are already supported without introducing a new type.

OTOH:

w = A[valid_A_indexes]

will copy A's data, and subsequent use of 

w[:] = something

will not update A.

Is this the reason for wanting the ignored data feature?