[Numpy-discussion] matrix indexing question
Paulo Jose da Silva e Silva
pjssilva@ime.usp...
Sun Mar 25 12:48:44 CDT 2007
Em Dom, 2007-03-25 às 13:07 -0400, Alan G Isaac escreveu:
> So this ::
>
> >>> x[1]
> matrix([[1, 0]])
>
> feels wrong. (Similarly when iterating across rows.)
> Of course I realize that I can just ::
>
> >>> x.A[1]
> array([1, 0])
>
> but since the above keeps feeling wrong I felt I should
> raise this as a possible design issue, better discussed
> early than latter.
I think the point here is that if you are using matrices, then all you
"should" want are matrices, just like in MATLAB:
>> A = [1 2; 3 4]
A =
1 2
3 4
>> b = A(1, :)
b =
1 2
>> size(b)
ans =
1 2
>> b = A(:, 1)
b =
1
3
>> size(b)
ans =
2 1
>> b = 1
b =
1
>> size(b)
ans =
1 1
You see, rows, columnes, and even numbers, are treated as matrices.
Paulo
--
Paulo José da Silva e Silva
Professor Assistente do Dep. de Ciência da Computação
(Assistant Professor of the Computer Science Dept.)
Universidade de São Paulo - Brazil
e-mail: rsilva@ime.usp.br Web: http://www.ime.usp.br/~rsilva
Teoria é o que não entendemos o (Theory is something we don't)
suficiente para chamar de prática. (understand well enough to call practice)
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