[Numpy-discussion] matrix indexing question

Colin J. Williams cjw@sympatico...
Mon Mar 26 11:05:18 CDT 2007


Alan G Isaac wrote:
> On Mon, 26 Mar 2007, "Colin J. Williams" apparently wrote: 
>> Perhaps things would be clearer if we thought of the 
>> constituent groups of data in a matrix as being themselves 
>> matrices. 
> 
> This "thinking of" is what you have suggested before.
> You need to explain why it is not begging the question.
> 
> Cheers,
> Alan Isaac

Perhaps it would now help if you redefined the question.

In an earlier posting, you appeared anxious that the matrix and the 
array behave in the same way.  Since they are different animals, I see 
sameness of behaviour as being lower on the list of desirables than 
fitting the standard ideas of matrix algebra.

Suppose that a is a row vector, b a column vector and A a conforming 
matrix then:
      a * A
      A * b
and  b.T * A are all acceptable operations.

One would expect the iteration over A to return row vectors, represented 
by (1, n) matrices.

Colin W.



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