Re: vectorisation and cell arrays

[Jaroslav Hajek]

On Fri, Mar 27, 2009 at 12:32 PM, Bertrand Roessli
<address@hidden> wrote:
> Hello,
>
> Does anybody know if it is possible to vectorize
> matrix operations (the matrices are stored in a cell array)
> on a vector and so to avoid looping over the elements
> of the cell? Thanks in advance
>
> For example
>
> a =
>
> {
>  [1,1] =
>
>     1   0   0
>     0  -1   0
>     0   0   1
>
>  [1,2] =
>
>     1   0   0
>    -1   0   0
>     0   0  -1
>
> e=[1;2;3];
>
> a{1}*e
>
> ans =
>
>   1
>  -1
>  -3
> works fine, but
> a{:}*e
>
> error: binary operator `*' not implemented for `cs-list' by `matrix'
> operations
>
>
> Bertrand Roessli
>
>

One alternative is to use cellfun(@mtimes, ...), but don't expect top
performance - there's a lot of overhead in calling a function handle.
If you could use a multi-dim array instead, you may be able to do it
using a single multiplication.

cheers

-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz