Re: How do I replace this for-loop?

[Rob Mahurin]

On Jul 4, 2008, at 5:48 PM, Robert Macy wrote:
> What's the best way to replace this for-loop?
>
> Given an array, n, of datapoints, such that:
>
> > > size(n)
> rows = 27000
> columns = 2
>
> where n(:,1) are all the integer x values, and
> n(:,2) are all the integer y values,
> both integer values are in the range of 1 to 101
>
> I slowly did it this way:
>
> output=zeros(101,101);
> for i=1:27000
>   output( n(i,1),n(i,2) ) = output( n(i,1),n(i,2) ) + 1;
> endfor

Well, there's hist2d :)
http://octave.svn.sourceforge.net/viewvc/octave/trunk/octave-forge/ 
main/plot/inst/hist2d.m?revision=HEAD&content-type=text/plain

> as you all know this is fairly slow.
> What's a simple way to replace this for-loop?
>
> Robert
>
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--
Rob Mahurin
Dept. of Physics & Astronomy
University of Tennessee         phone: 865 207 2594
Knoxville, TN 37996             email: address@hidden