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## vectorization

**From**: |
David Pruitt |

**Subject**: |
vectorization |

**Date**: |
Tue, 3 Dec 2002 13:51:14 -0600 |

In some work I'm now doing, I continually find the need to determine the
set of indices of vector A which contain elements of vector B - elements of
B will occur in A no more than once. Here's an example of what my code
looks like:
# contrived example
# vector A
i_num = [1:100];
# vector B
v_num = [ 1 3 5 12 ];
lt = length(v_num);
for i = 1:lt
idx(i) = find( i_num == v_num(i) );
endfor;
In this example, idx would of course be 1,3,5,12. So it's sort of a
two-dimensional "find". I'll just bet I'm doing this the hard way. Is
there another way without a for-loop? For the cases I'm seriously
concerned with, the vectors contain 5,000 to 15,000 elements.
Thanks,
David
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**vectorization**,
*David Pruitt* **<=**