This could be a bit faster.
x1<- matrix(NA,5,5)
diag(x1)<-0
x1[which(is.na(x1),arr.ind=TRUE)]<- as.vector(x)
#Speed comparison:
set.seed(585)
m1<- matrix(sample(1:40,4500*4499,replace=TRUE),ncol=4500)
system.time({
m2<- matrix(0,4500,4500)
indx<- which(m2==0,arr.ind=TRUE)
m2[indx[indx[,1]!=indx[,2],]]<- as.vector(m1)
})
#user system elapsed
# 3.304 0.616 3.927
system.time({
m2New<- matrix(NA,4500,4500)
diag(m2New)<-0
m2New[which(is.na(m2New),arr.ind=TRUE)]<- as.vector(m1)
})
# user system elapsed
# 2.268 0.424 2.699
system.time({
m3 <- matrix(0,4500,4500)
m3[upper.tri(m3)] <- m1[upper.tri(m1)]
m3[lower.tri(m3)] <- m1[lower.tri(m1, diag=TRUE)]
})
#user system elapsed
# 4.208 0.572 4.790
identical(m2,m2New)
#[1] TRUE
identical(m2,m3)
#[1] TRUE
A.K.
----- Original Message -----
From: arun <smartpink...@yahoo.com>
To: Martin Batholdy <batho...@googlemail.com>
Cc: R help <r-help@r-project.org>; Richard Heiberger <r...@temple.edu>
Sent: Saturday, August 3, 2013 9:10 PM
Subject: Re: [R] add diagonal to matrix
You could also try:
x1<-matrix(0,5,5)
indx<-which(!is.na(x1),arr.ind=TRUE)
x1[indx[indx[,1]!=indx[,2],]]<- as.vector(x)
#Speed comparison:
set.seed(48)
m1<- matrix(sample(1:40,4500*4499,replace=TRUE),ncol=4500)
m2<- matrix(0,4500,4500)
system.time({
indx<- which(m2==0,arr.ind=TRUE)
m2[indx[indx[,1]!=indx[,2],]]<- as.vector(m1)
})
# user system elapsed
# 3.376 0.648 4.037
m3 <- matrix(0,4500,4500)
system.time({
m3[upper.tri(m3)] <- m1[upper.tri(m1)]
m3[lower.tri(m3)] <- m1[lower.tri(m1, diag=TRUE)]
})
# user system elapsed
# 4.236 0.460 4.709
identical(m2,m3)
#[1] TRUE
A.K.
----- Original Message -----
From: Martin Batholdy <batho...@googlemail.com>
To: "r-help@r-project.org" <r-help@r-project.org>
Cc:
Sent: Saturday, August 3, 2013 2:54 PM
Subject: [R] add diagonal to matrix
Hi,
I have a 5 columns x 4 rows matrix and would like to add a diagonal of zeros so
that I end up with a 5x5 matrix.
x <- matrix(1:20, 4,5)
what is the easiest way to accomplish this in R?
thanks for any suggestions!
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
