retain dimensions for numpy slice
duncan smith
duncan at invalid.invalid
Mon Oct 24 13:36:44 EDT 2016
Hello,
I have several arrays that I need to combine elementwise in
various fashions. They are basically probability tables and there is a
mapping of axes to variables. I have code for transposing and reshaping
that aligns the variables / axes so the usual broadcasting rules achieve
the desired objective. But for a specific application I want to avoid
the transposing and reshaping. So I've specified arrays that contain the
full dimensionality (dimensions equal to the total number of variables).
e.g.
Arrays with shape,
[1,3,3] and [2,3,1]
to represent probability tables with variables
[B,C] and [A,B].
One operation that I need that is not elementwise is summing over axes,
but I can use numpy.sum with keepdims=True to retain the appropriate shape.
The problem I have is with slicing. This drops dimensions. Does anyone
know of a solution to this so that I can e.g. take an array with shape
[2,3,1] and generate a slice with shape [2,1,1]? I'm hoping to avoid
having to manually reshape it. Thanks.
Duncan
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