On Wed, Mar 26, 2008 at 11:01 AM, Jason Grout
<[EMAIL PROTECTED]> wrote:
>
> Ryan Hinton brought up a good point at #2651:
>
> Currently, matrix(3,{(1,1): 2}) gives the 3x2 sparse matrix
>
> [0 0]
> [0 2]
> [0 0]
>
>
> However, for other cases, if we specify just the number of rows, the
> returned matrix is square (except when we are giving all the entries of
> the matrix and there aren't enough entries). So:
>
> Should the above command return the following instead?
>
> [0 0 0]
> [0 2 0]
> [0 0 0]
>
> Sorry for bringing up the nitpicky corner cases, but since matrix() is
> used in a huge number of things, we don't want to mess something up when
> we replace the constructor.
I very strongly agree that the output of matrix(3,{(1,1): 2}) should be the
sparse matrix:
[0 0 0]
[0 2 0]
[0 0 0]
BTW, there should be an example in the docstring for matrix that illustrates
how to make a dense matrix given a dictionary as input. E.g.,
sage: matrix(2,{(1,1):5},sparse=False).parent()
Full MatrixSpace of 2 by 2 dense matrices over Integer Ring
-- William
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