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Hi,

Just a small correction... it is the number of *lines* from the left matrix
that must
match the number of *columns* from the right matrix.

Kind Regards

J. Augusto

On 12/21/06, Vincent Fourmond <vincent.fourmond / 9online.fr> wrote:
>
> seepee wrote:
> > On Thu, 21 Dec 2006 09:12:47 +0200, seepee wrote:
> >
> >> Does anyone know of a functional Matrix math class for ruby that could
> >> multiply, add and substract 3x2 or larger matrices.
> >>
> >> The matrix.rb that is in Ruby API cannot multiply anything larger than
> 2x2
> >> matrices, which makes it useless for 2D or 3D graphics (for instance).
> >>
> >> SP
> >
> > Problem:
> > go to terminal, and type "irb" or "irb1.8"
> >
> >> require 'matrix' #or require >rubylibrarypath/matrix.rb
> >> p Matrix[ [25, 93, 33], [0, -1, 66] ] * Matrix[ [1, 53, 33], [1, -21,
> 77]
>
>   Err... Have you done matrix computations for a long time ? You need
> that the number of *columns* from the left matrix matches the number of
> *lines* from the right matrix. If you try to multiply two 3x2 matrices,
> it is rather encouraging that Matrix refuses it...
>
>   Try transposing your matrix first, if that is what you need. Are you
> dealing with transformation matrices (which are not real matrices) ?
>
>         Vincent
>
> --
> Vincent Fourmond, PhD student
> http://vincent.fourmond.neuf.fr/
>
>

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