[Numpy-discussion] untenable matrix behavior in SVN

[Keith Goodman]

On Tue, Apr 29, 2008 at 2:18 PM, Anne Archibald
<peridot.faceted at gmail.com> wrote:
> On 29/04/2008, Keith Goodman <kwgoodman at gmail.com> wrote:
>  > In my use i is most commonly an array (i = M.where(y.A)[0] where y is
>  >  a nx1 matrix), sometimes a list, and in ipython when debugging or
>  >  first writing the code, a scalar. It would seem odd to me if x[i,:]
>  >  returned different types of objects based on the type of i:
>  >
>  >  array index
>  >  idx = M.where(y.A)[0] where y is a nx1 matrix
>  >  x[dx,:] -->  matrix
>  >
>  >  list index
>  >  idx = [0]
>  >  x[idx,:] --> matrix?
>  >
>  >  scalar index
>  >  idx = 0
>  >  x[idx,:] --> not matrix
>
>  It is actually pretty unreasonable to hope that
>
>  A[0]
>
>  and
>
>  A[[1,2,3]]
>  or
>  A[[True,False,True]]
>
>  should return objects of the same rank.

Why it unreasonable to hope that

x[0,:]

and

x[0, [1,2,3]]

or

x[0, [True,False,True]]

where x is a matrix, continue to return matrices?