Hi,
May be this:
N <- 1000
M <- 5
P <- 5000
set.seed(15)
A <- matrix(runif(N,1,1000),nrow=N,ncol=M)
set.seed(425)
B <- matrix(runif(M,1,1000),nrow=P,ncol=M)
Marius.3.0<-function(A,B){do.call(cbind,lapply(split(B,row(B)),function(x)
colSums(x>=t(A))==ncol(A)))}
system.time(Marius.3.0(A,B))
# user system elapsed
# 0.524 0.000 0.523
system.time(Marius.2.0(A,B))
# user system elapsed
# 0.972 0.236 1.212
system.time(perhaps(A,B))
# user system elapsed
#1.232 0.244 1.482
system.time(Marius(A,B))
# user system elapsed
# 19.266 0.000 19.298
With the toy example:
A <- rbind(matrix(1:4, ncol=2, byrow=TRUE), c(6, 2)) # (3, 2) matrix
B <- matrix(1:10, ncol=2) # (5, 2) matrix
ind <- apply(B, 1, function(b) apply(A, 1, function(a) all(a <= b)))
ind
# [,1] [,2] [,3] [,4] [,5]
#[1,] TRUE TRUE TRUE TRUE TRUE
#[2,] FALSE FALSE TRUE TRUE TRUE
#[3,] FALSE FALSE FALSE FALSE FALSE
Marius.3.0(A,B)
# 1 2 3 4 5
#[1,] TRUE TRUE TRUE TRUE TRUE
#[2,] FALSE FALSE TRUE TRUE TRUE
#[3,] FALSE FALSE FALSE FALSE FALSE
str(ind)
# logi [1:3, 1:5] TRUE FALSE FALSE TRUE FALSE FALSE ...
str(Marius.3.0(A,B))
# logi [1:3, 1:5] TRUE FALSE FALSE TRUE FALSE FALSE ...
#- attr(*, "dimnames")=List of 2
#..$ : NULL
#..$ : chr [1:5] "1" "2" "3" "4" ...
A.K.
----- Original Message -----
From: Marius Hofert <marius.hof...@math.ethz.ch>
To: R-help <r-help@r-project.org>
Cc:
Sent: Saturday, December 8, 2012 6:28 AM
Subject: [R] How to efficiently compare each row in a matrix with each row in
another matrix?
Dear expeRts,
I have two matrices A and B. They have the same number of columns but possibly
different number of rows. I would like to compare each row of A with each row
of B and check whether all entries in a row of A are less than or equal to all
entries in a row of B. Here is a minimal working example:
A <- rbind(matrix(1:4, ncol=2, byrow=TRUE), c(6, 2)) # (3, 2) matrix
B <- matrix(1:10, ncol=2) # (5, 2) matrix
( ind <- apply(B, 1, function(b) apply(A, 1, function(a) all(a <= b))) ) # (3,
5) = (nrow(A), nrow(B)) matrix
The question is: How can this be implemented more efficiently in R, that is, in
a faster way?
Thanks & cheers,
Marius
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
