[Numpy-discussion] matrices in 1.1

Stéfan van der Walt stefan@sun.ac...
Sat Mar 22 10:40:55 CDT 2008


On Sat, Mar 22, 2008 at 4:40 PM, Stéfan van der Walt <sjvdwalt@gmail.com> wrote:
> Hi Alan
>
>
>  On Fri, Mar 21, 2008 at 7:11 PM, Alan G Isaac <aisaac@american.edu> wrote:
>  > On Fri, 21 Mar 2008, Stéfan van der Walt apparently wrote:
>  >  > The last I remember, we considered adding RowVector,
>  >  > ColumnVector and letting slices out of a matrix either be
>  >  > one of those or a matrix itself.
>  >
>  >  There was a subsequent discussion.
>
>  If there was, I still don't remember the result being the one you
>  suggested (could be my bad memory, but maybe you can post a link as a
>  reminder).
>
>
>  >  > I simply don't see a Matrix as a container of ndarrays
>  >  That is hardly an argument.
>
>  Not an argument, just my opinion or perspective.  In the matrix world,
>  everything has a minimum dimension of 2, so I don't see how you can
>  contain ndarrays in a matrix.
>
>
>  >  Remember, any indexing that when applied to an 2d array
>  >  would produce a 2d array will when applied to a matrix
>  >  still produce a matrix.
>
>  Sure.
>
>
>  >  This is really just principle of least surprise.
>
>  Or not, depending on where you come from.  I'd expect indexing
>  operations that produce 1D-arrays on ndarrays to produce 2D-arrays on
>  matrices.
>
>
>  >  PS Are you a *user* of matrices?
>
>  No, I'm not (I love the consistency of the ndarray approach, and
>  broadcasting always does the Right Thing (TM)).  Although I do
>  sometimes use matrices when I'm lazy to apply dot, i.e.
>
>  A,B,C,D = [np.asmatrix(a) for a in [arr1,arr2,arr3,arr4]]
>  result = (A*B*C*D).A
>
>  Regards
>  Stéfan
>


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