[R] Vector comparison to matrix

[Prof Brian Ripley]

Probably you use the idea from unique.matrix, that is

1) form a string from each row and
2) call match() to see which strings match your pattern row.

On Sun, 14 Aug 2005, Todd Remund wrote:

> I am looking for a fast way to count the number of rows in a matrix are
> identical to a pattern vector.  For example, if I am interested in counting
> the number of row vectors in a matrix that are identical to (1,2,3) what
> would I do?  I have tried the identical statement in a loop but this is far
> too slow.  I have a very large matrix and need to avoid loops at all costs.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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