This might also work:
roweqv2<- function(m,v){indx<-1+Reduce("+",lapply(seq_len(ncol(m)),function(i) (2^i)*(m[,i]==v[i])))
??? ??? ??? ?which(indx==max(indx))}???
roweqv2(m,v)
#[1] 2
?system.time(res2<-roweqv2(m1,v1))
#?? user? system elapsed
? #0.008?? 0.000?? 0.008
?identical(res,res2)
#[1] TRUE
#On a bigger dataset
set.seed(248)
?m1<-matrix(sample(1:15,3e7,replace=TRUE),ncol=3)
?v1<- c(10,12,4)
?system.time(res<- roweqv(m1,v1))
#?? user? system elapsed
# 12.404?? 1.248? 13.677
? system.time(res2<-roweqv2(m1,v1))
#?? user? system elapsed
?# 0.760?? 0.312?? 1.076
identical(res,res2)
#[1] TRUE
A.K.
----- Original Message -----
From: arun <smartpink111 at yahoo.com>
To: Sachinthaka Abeywardana <sachin.abeywardana at gmail.com>
Cc: R help <r-help at r-project.org>
Sent: Wednesday, June 26, 2013 3:26 PM
Subject: Re: [R] match rows of R
Hi,
Try:
?roweqv<- function(m,v) which(!is.na(match(interaction(as.data.frame(m),drop=TRUE),paste(v,collapse="."))))
v<- c(2,5,8)
roweqv(m,v)
#[1] 2
set.seed(24)
m1<-matrix(sample(1:15,3e5,replace=TRUE),ncol=3)
v1<- c(10,12,4)
?system.time(res<- roweqv(m1,v1))
? # user? system elapsed
? #0.132?? 0.000?? 0.130
res
# [1]???? 5?? 381? 2760? 3793? 9667 16881 18866 21219 24961 36220 38366 54382
#[13] 54951 55825 57167 67636 70713 71087 73284 82797 83255 85748 86216 86690
#[25] 93120 95399 96370
head(m1[res,])
#???? [,1] [,2] [,3]
#[1,]?? 10?? 12??? 4
#[2,]?? 10?? 12??? 4
#[3,]?? 10?? 12??? 4
#[4,]?? 10?? 12??? 4
#[5,]?? 10?? 12??? 4
#[6,]?? 10?? 12??? 4
v2<- c(20,5,4)
roweqv(m1,v2)
#integer(0)
A.K.
----- Original Message -----
From: Sachinthaka Abeywardana <sachin.abeywardana at gmail.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc:
Sent: Wednesday, June 26, 2013 4:03 AM
Subject: [R] match rows of R
Hi all,
What would be an efficient way to match rows of a matrix to a vector?
ex:
m<-matrix(1:9, nrow=3)
m? ?? [,1] [,2] [,3]
[1,]? ? 1? ? 4? ? 7
[2,]? ? 2? ? 5? ? 8
[3,]? ? 3? ? 6? ? 9
#################################
which(m==c(2,5,8))? ? ? ? # I want this to return 2
######################
Thanks,
Sachin
??? [[alternative HTML version deleted]]
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