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

[Neal Becker]

Charles R Harris wrote:

> On Wed, Mar 7, 2012 at 1:05 PM, Neal Becker <ndbecker2 at gmail.com> wrote:
> 
>> 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?
>>
> 
> Suppose you are working with plotted data and want to turn points on/off by
> clicking on them interactively to see how that affects a fit. Why make
> multiple copies, change sizes, destroy data, and all that nonsense? Just
> have the click update the mask and redraw.
> 
> Chuck

But does

some_func (A[valid_data_mask])

actually perform a copy?