Re: [R] Vector comparison to matrix

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Mon 15 Aug 2005 - 16:42:59 EST

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@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Mon Aug 15 16:51:02 2005

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