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From: <HIDDEN>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Find function
Date: Wed, 26 Nov 2008 00:23:01 +0000 (UTC)
Organization: University of Hawaii, Manoa
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Xref: news.mathworks.com comp.soft-sys.matlab:503214

Roger,
Thanks for the help, this solution worked great!  Thanks to everyone else who replyed.
ML

"Roger Stafford" <ellieandrogerxyzzy@mindspring.com.invalid> wrote in message <gga9c9\$l1c\$1@fred.mathworks.com>...
> "Gordon " <mloomis@gmail.com> wrote in message <gg8c2k\$s8d\$1@fred.mathworks.com>...
> > I&#8217;m attempting to run a find command on two vectors A and B, I want to find the number of occurrences in vector a  that are <= every occurrence in vector b.  I can do this easily with a for loop, but it takes forever to run on large vectors.  Here is my code&#8230;
> >
> > y=zeros(length(a),1);
> > for i = 1:length(a)
> >    a1 = a(i);
> >    y(i) = length(find(b <= a1));
> > end
> >
> > a= [1;1;2;3;4;5;7;9;3]
> > b=[ 1;2;3;4;1;2;3;3;3;4;1;1;2;3;4]
> > y= [4;4;7;12;15;15;15;15;12]
> >
> > This works fine with small vectors, but I want to do this with very large vectors.  Is there any way to do this in Matlab without using the For Loop?
> >
> > Any help would be appreciated.
>
>   I realized belatedly that the code I sent you has its inequality testing backwards with respect to the for-loop code you gave.  Here is the corrected version.  It now assumes that a and b are column vectors.  For large arrays it should be considerably faster than your for-loop method.
>
>  [p,p] = sort([b;a]);
>  t = cumsum(p<=length(b));
>  q = (1:length(p)); q(p) = q;
>  y = t(q(length(b)+1:end));
>
> Roger Stafford
>

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