[Numpy-discussion] matrix indexing question

Bill Spotz wfspotz@sandia....
Thu Mar 29 17:13:44 CDT 2007


What I envisioned was that M[i,:] would return a row_vector and M 
[:,j] would return a column_vector, because this would be symmetric  
behavior.  M[i], by convention, would behave the same as M[i,:].

But then I personally don't distinguish between "python indexing" and  
"numpy indexing".  In both cases, __getitem__() (or __setitem__()) is  
called.  For multiple indexes, the index object is a tuple.

In any case, the behavior of "numpy indexing" as I have proposed it  
would return an object that inherits from matrix, thus would BE a  
matrix, although it would behave like an array.

On Mar 29, 2007, at 3:24 PM, Alan G Isaac wrote:

> On Tue, 27 Mar 2007, Zachary Pincus apparently wrote:
>> Now, Bill offers up a different suggestion: indexing
>> M yields neither a matrix nor an array, but a class that
>> operates more or less like an array, except insofar as it
>> interacts with other matrix objects, or other objects of
>> similar classes. I'm interested in hearing more about
>> this, what trade-offs or other compromises it might
>> involve.
>
> So would you agree that in this case M[0] and M[0,:] would
> have to be different things?  Or would you then want even
> such numpy indexing not to produce matrices??
>
> Cheers,
> Alan Isaac

** Bill Spotz                                              **
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