I haven't looked at the size-time relationship, but im2 (below) is faster than
your
function on at least one example:
intersectMat <- function(mat1, mat2)
{
#mat1 and mat2 are both deduplicated
nr1 <- nrow(mat1)
nr2 <- nrow(mat2)
mat2[duplicated(rbind(mat1, mat2))[(nr1 + 1):(nr1 + nr2)], , drop=FALSE]
}
im2 <- function(mat1, mat2)
{
stopifnot(ncol(mat1)==2, ncol(mat1)==ncol(mat2))
toChar <- function(twoColMat) paste(sep="\1", twoColMat[,1], twoColMat[,2])
mat1[match(toChar(mat2), toChar(mat1), nomatch=0), , drop=FALSE]
}
> m1 <- cbind(1:1e7, rep(1:10, len=1e7))
> m2 <- cbind(1:1e7, rep(1:20, len=1e7))
> system.time(r1 <- intersectMat(m1,m2))
user system elapsed
430.37 1.96 433.98
> system.time(r2 <- im2(m1,m2))
user system elapsed
27.89 0.20 28.13
> identical(r1, r2)
[1] TRUE
> dim(r1)
[1] 5000000 2
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf
> Of c char
> Sent: Monday, July 29, 2013 4:04 PM
> To: r-help@r-project.org
> Subject: [R] Intersecting two matrices
>
> Dear all,
>
> I am interested to know a faster matrix intersection package for R handles
> intersection of two integer matrices with ncol=2. Currently I am using my
> homemade code adapted from a previous thread:
>
>
> intersectMat <- function(mat1, mat2){#mat1 and mat2 are both
> deduplicated nr1 <- nrow(mat1) nr2 <- nrow(mat2)
> mat2[duplicated(rbind(mat1, mat2))[(nr1 + 1):(nr1 + nr2)], ]}
>
>
> which handles:
> size A= 10578373
> size B= 9519807
> expected intersecting time= 251.2272
> intersecting for corssing MPRs took 409.602 seconds.
>
> scale a little bit worse than linearly but atomic operation is not good.
> Wonder if a super fast C/C++ extension exists for this task. Your ideas are
> appreciated.
>
> Thanks!
>
> [[alternative HTML version deleted]]
>
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