[Numpy-discussion] matrix indexing question
Colin J. Williams
cjw@sympatico...
Sun Mar 25 18:20:21 CDT 2007
Alan G Isaac wrote:
>> Em Dom, 2007-03-25 Ã s 13:07 -0400, Alan G Isaac escreveu:
>>> >>> x[1]
>>> matrix([[1, 0]])
>>> feels wrong. (Similarly when iterating across rows.)
>
>
> On Sun, 25 Mar 2007, Paulo Jose da Silva e Silva apparently wrote:
>> I think the point here is that if you are using matrices,
>> then all you "should" want are matrices, just like in
>> MATLAB:
>> >> b = A(1, :)
>> b =
>> 1 2
>
>
> Yes, that is the idea behind this, which I am also
> accustomed to from GAUSS. But note again that the Matlab
> equivalent ::
>
> >>> x=N.mat('1 2;3 4')
> >>> x[0,:]
> matrix([[1, 2]])
>
> does provide this behavior. The question I am raising
> is a design question and is I think really not addressed
> by the rule of thumb you offer. Specifically, that rule
> of thumb if it is indeed the justification of ::
>
> >>> x[1]
> matrix([[3, 4]])
>
> finds itself in basic conflict with the idea that I ought to
> be able to iterate over the objects in an iterable container.
>
> I mean really, does this not "feel" wrong? ::
>
> >>> for item in x: print item.__repr__()
> ...
> matrix([[1, 2]])
> matrix([[3, 4]])
>
> Cheers,
> Alan Isaac
>
>
Perhaps this would be clearer with:
>>> for rowVector in x: print item.__repr__()
...
matrix([[1, 2]])
matrix([[3, 4]])
Colin W.
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