[Numpy-discussion] matrix wart

Christopher Barker Chris.Barker@noaa....
Fri Feb 22 10:48:46 CST 2008


Travis E. Oliphant wrote:
> to behave as you described in your previous post:  where M[i] returned a 
> 1-d array

My thoughts on this:

As Konrad suggested, row vectors and column vectors are different beasts 
,and both need to be easily and intuitively available.

M[i] returning a 1-d array breaks this -- that's what raw numpy arrays 
do, and I like it, but it's not so natural for linear algebra. If we 
really want to support matrixes, then no, M[i] should not return a 1-d 
array -- what is a 1-d array  mean in the matrix/linear algebra context?

It makes me think that M[i] should not even be possible, as you would 
always want one of:

row vector:  M[i,:]
column vector: M[:,i]
element: M[i,j]

I do like the idea of a row/column vectors being different objects than 
matrices, then you could naturally index the elements from them.

If you really want a 1-d array, you can always do:

M.A[i]

What if you want to naturally iterate through all the rows, or all the 
columns? what about:

for row in M.rows

for column in M.columns

M.rows and M.columns would be iterators.

-Chris

-- 
Christopher Barker, Ph.D.
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