[R] Vector comparison to matrix

[Sigurdur Jonsson]

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:

target<-c(1,2,3)
A<-matrix(sample(1:3,300000,replace=TRUE),ncol=3)

# 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.

Siggi

> version
         _
platform i686-redhat-linux-gnu
arch     i686
os       linux-gnu
system   i686, linux-gnu
status
major    2
minor    0.0
year     2004
month    10
day      04
language R

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

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Sigurður Þór Jónsson	/	Sigurdur Tor Jonsson
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