Hi, On Fri, Oct 28, 2011 at 1:52 PM, Benjamin Root <ben.root@ou.edu> wrote:
On Fri, Oct 28, 2011 at 3:22 PM, Matthew Brett <matthew.brett@gmail.com> wrote:
Hi,
On Fri, Oct 28, 2011 at 1:14 PM, Benjamin Root <ben.root@ou.edu> wrote:
On Fri, Oct 28, 2011 at 3:02 PM, Matthew Brett <matthew.brett@gmail.com> wrote:
You and I know that I've got an array with values [99, 100, 3] and a mask with values [False, False, True]. So maybe I'd like to see what happens if I take off the mask from the second value. I know that's what I want to do, but I don't know how to do it, because you won't let me manipulate the mask, because I'm not allowed to know that the NA values come from the mask.
The alterNEP is just saying - please - be straight with me. If you're doing masking, show me the mask, and don't try and hide that there are stored values underneath.
Considering that you have admitted before to not regularly using masked arrays, I seriously doubt that you would be able to judge whether this is a significant detriment or not. My entire point that I have been making is that Mark's implementation is not the same as the current masked arrays. Instead, it is a cleaner, more mature implementation that gets rid of extraneous "features".
This may explain why we don't seem to be getting anywhere. I am sure that Mark's implementation of masking is great. We're not talking about that. We're talking about whether it's a good idea to make masking look as though it is implementing the ABSENT idea. That's what I think is confusing, and that's the conversation I have been trying to pursue.
Best,
Matthew
Sorry if I came across too strongly there. No disrespect was intended.
I wasn't worried about the disrespect. It's just I feel the discussion has not been to the point.
Personally, I think we are getting somewhere. We have been whittling away what it is that we do agree upon, and have begun to specify *exactly* what it is that we disagree on. I have understand your concern, and -- like I said in my previous email -- it makes sense from the perspective of numpy.ma users have had up to now.
But I'm not a numpy.ma user, I'm just someone who knows that what you are doing is masking out values. The fact that I do not use numpy.ma points out that it's possible to find this highly counter-intuitive without prior bias.
But, I re-raise my point that I have been making about the need to re-think masked arrays. If we consider masks as advanced slicing or boolean indexing, then being unable to access the underlying values actually makes a lot of sense.
Consider it a contract when I pass a set of data with only certain values exposed. Because I passed the data with only those values exposed, then it must have been entirely my intention to let the function know of only those values. It would be a violation of that contract if the function obtained those masked values. If I want to communicate both the original values and a particular mask, then I pass the array and a view with a particular mask.
This is the old discussion about what Python users expect. I think they expect to be treated as adults. That is, breaking the contract should not be easy to do by accident, but it should be allowed.
Maybe it would be helpful that an array can never have its own mask, but rather, only views can carry masks?
In conclusion, I submit that this is largely a problem that can be solved with the proper documentation. New users who never used numpy.ma before do not have to concern themselves with the old way of thinking and are just simply taught what masked arrays "are". Meanwhile, a special section of the documentation should be made that teaches numpy.ma users how masked arrays "should be".
I don't think documentation will solve it. In a way, the ideal user is someone who doesn't know what's going on, because, for a while, they may not realize that when they thought they were doing assignment, in fact they are doing masking. Unfortunately, I suspect almost everyone using these things will start to realize that, and then they will start getting confused. I find it confusing, and I believe myself to understand the issues pretty well, and be of numpy-user-range comprehension powers. See you, Matthew