From: Spencer Graves <spencer.graves_at_pdf.com>

Date: Sun 04 Jul 2004 - 01:27:43 EST

R-help@stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jul 04 01:30:30 2004

Date: Sun 04 Jul 2004 - 01:27:43 EST

What have you tried? Have you considered something like the following:

n <- 4 m <- 3 k <- 2 A <- array(1, dim=c(n, k)) B <- array(1, dim=c(m,k))

BinA <- rep(NA, m)

tA <- t(A)

for(i in 1:m){

BinA[i] <- sum(apply(B[i,]==tA, 2, sum)==k)
}

> BinA

[1] 4 4 4

hope this helps. spencer graves

Ravi Varadhan wrote:

*>Hi:
**>
*

>I have two matrices, A and B, where A is n x k, and B is m x k, where n >> m >> k. Is there a computationally fast way to count the number of times each row (a k-vector) of B occurs in A? Thanks for any suggestions.

*>
**>Best,
**>Ravi.
**>
**> [[alternative HTML version deleted]]
**>
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R-help@stat.math.ethz.ch mailing list

https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sun Jul 04 01:30:30 2004

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