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## Re: how to vectorize it

 From: Doug Stewart Subject: Re: how to vectorize it Date: Sun, 21 Jul 2019 18:12:01 -0400

On Sun, Jul 21, 2019 at 5:51 PM shall689 <address@hidden> wrote:
shivax wrote
> hi, see this code:
>
>  input for example:
>
>  ris=[1 0 0;0 1 0;1 0 0; 0 1 1]
>  tit=[0 1 0 0]
>
>  tic
>  bb=0;
>  for hh=1:columns(ris)
>   bb=0;
>   for gg=1:rows(ris)
>     if tit(gg)
>          bb=0;
>         if ris(gg,hh)
>             bb=1;
>      endif
>     endif
>      ris(gg,hh)=bb;
>    endfor
>  endfor
>  toc

>
> it's possible to avoid loop?
>
>
>
> --
> Sent from:
> http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html

If you explain what you are trying to do, there might be a better way.

Here is what I understand of your very interesting problem.  Each row in the
tit vector is associated with a row in the ris matrix.  All ris rows up
until the first tit row that equals 1 should be set to zero.  When a tit row
= 1, the associated row in the ris vector should be copied and over write
all ris rows until tit row equals 1 again.

I haven't been able to solve the problem, but I think repmat and find might

find(tit==1) will find the index of all the rows in tit that are equal to 1
and repmat(ris(row,:),row,1) can be used to repeat a specific row in ris.

If you can find the difference between the row index values of tit==1, you
can determine how many times to repeat a specific row.

If you find out how to vectorize this problem, could you please post the
solution.

Thanks,
Stephen

--
Sent from: http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html

--
DAS