[R] Vector comparison to matrix

From: Sigurdur Jonsson <sigurdur_at_hafro.is>
Date: Tue 16 Aug 2005 - 20:47:06 EST

Hi Todd and list,

I see you have received a few suggestions, here's another:

# set up data: your vector and an a 3x300000 matrix with a few
# matching lines:


# count matches:

nMatches<-sum(apply(A,1,function(x,target)   all.equal(x,target),target)=="TRUE")

# by applying a simple function, which takes 'target' as an 'extra'
# argument, to the rows of A. The function returns a vector of
# differences and 'TRUE'-s, the latter of which can be counted.

This took 1-2 minutes on my >3 year old laptop.


> version

platform i686-redhat-linux-gnu

arch     i686
os       linux-gnu

system i686, linux-gnu
major 2
minor 0.0
year 2004
month 10
day 04
language R

Yeah, I know, an update is (over)due.

Sigurđur Ţór Jónsson	/	Sigurdur Tor Jonsson
E-mail:				<sigurdur@hafro.is>			
Snail-mail:			Marine Research Institute,
				P.O. Box 1390,
				121 Reykjavik,Iceland
Telephone (direct line):	+354 5752093
Telephone (switchboard):	+354 5752000 
Fax:				+354 5752001

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Received on Tue Aug 16 20:56:12 2005

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