Re: [ublas] Sub-matrix Question

Subject: Re: [ublas] Sub-matrix Question
From: David Bellot (david.bellot_at_[hidden])
Date: 2010-10-29 02:45:08

look at matrix_indirect:http://www.boost.org/libs/numeric/ublas/doc/html/classboost_1_1numeric_1_1ublas_1_1matrix__indirect.html
You can make any submatrix with that.

David

On Fri, Oct 29, 2010 at 07:21, Bin Dai <daibin84_at_[hidden]> wrote:

> Hi,
>
> I am working a a project that I need to use a sub-matrix of a given
> matrix, the MATLAB code is as follows:
>
> >> M = reshape(1:18, 3, 6)
>
> M =
>
>     1     4     7    10    13    16
>     2     5     8    11    14    17
>     3     6     9    12    15    18
>
> >> subM = M(2:3, [1, 4, 6])
>
> subM =
>
>     2    11    17
>     3    12    18
>
>
> the subM is the one I want. I understand there are very convenient
> tools 'range' and 'slice' but I am trying to get a general one such as
> [1, 4, 6] in the previous example.
> In addition, I read the thread on
> http://archives.free.net.ph/message/20100723.123350.753d32ba.en.html
> using indirect_array but I want a better one such as indexing the rows
> with range by the columns with indirect_array.
>
> I know I can do it by constructing a new matrix with elements from the
> original matrix but I want a more efficient one so I can save a little
> memory when dealing with large=scale matrix.
>
> Thanks
>
> Bin
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>

-- 
David Bellot, PhD
david.bellot_at_[hidden]
http://david.bellot.free.fr