[Numpy-discussion] in the NA discussion, what can we agree on?

Gary Strangman strang at nmr.mgh.harvard.edu
Fri Nov 4 09:29:05 EDT 2011

> > non-destructive+propagating -- it really depends on exactly what
> > computations you want to perform, and how you expect them to work. The
> > main difference is how reduction operations are treated. I kind of
> > feel like the non-propagating version makes more sense overall, but I
> > don't know if there's any consensus on that.
> I think this is further evidence for my idea that a mask should not be
> undone, but is non destructive.  If you want to be able to access the values
> after masking, have a view, or only apply the mask to a view.

OK, so my understanding of what's meant by propagating is probably 
incomplete (and is definitely still fuzzy). I'm a little confused by the 
phrase "a mask should not be undone" though. Say I want to perform a 
statistical analysis or filtering procedure excluding and (separately) 
including a handful of outliers? Isn't that a natural case for undoing a 
mask? Or did you mean something else?

I think I understand the "use a view" option above, though I don't see how 
one could apply a mask only to a view. What if my view is every other row 
in a 2D array, and I want to mask the last half of this view? What is the 
state of the original array once the mask has been applied?

(If this is derailing the progress of this thread, feel free to ignore 


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