Re: Mask the matrix

[Jaroslav Hajek]

On Tue, May 12, 2009 at 4:59 PM, Przemek Klosowski
<address@hidden> wrote:
> You can do it this way: a(:,!sum(a==0))
>
> Explanation:
>
>  - a==0 is a matrix with '1' where your data has zeros
>  - sum(a==0) adds them up columnwise, so it will be zero only if no zeros 
> were in that column.
>  - a(:,!sum(a==0)) selects full columns based on a boolean mask created from 
> the prev. expression

a slightly better expression is
a(:, all (a)).
because, in general, `all' and `any' are faster than `sum', because
they use short-circuiting.

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