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Re: how to vectorize it

From: shall689
Subject: Re: how to vectorize it
Date: Sun, 21 Jul 2019 16:51:49 -0500 (CDT)

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:

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
be helpful.

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


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