I quickly looked at it, and the difference comes from:
n <- 5e3
system.time(x <- array(0, c(n, n))) # from diag()
system.time(x <- matrix(0, n, n)) # from Rdiag()
Replaced in R-devel.
Best,
Uwe Ligges
On 07.06.2012 12:11, Spencer Graves wrote:
On 6/7/2012 2:27 AM, Rui Barradas wrote:
Hello,
To my great surprise, on my system, Windows 7, R 15.0, 32 bits, an R
version is faster!
I was also surprised, Windows 7, R 2.15.0, 64-bit
> rbind(diag=t1, Rdiag=t2, ratio=t1/t2)
user.self sys.self elapsed user.child sys.child
diag 0.72 0.080000 0.81 NA NA
Rdiag 0.09 0.030000 0.12 NA NA
ratio 8.00 2.666667 6.75 NA NA
>
> sessionInfo()
R version 2.15.0 (2012-03-30)
Platform: x86_64-pc-mingw32/x64 (64-bit)
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] splines stats graphics grDevices utils datasets methods
[8] base
other attached packages:
[1] fda_2.2.9 Matrix_1.0-6 lattice_0.20-6 zoo_1.7-7
loaded via a namespace (and not attached):
[1] grid_2.15.0 tools_2.15.0
>
Spencer
Rdiag <- function(n){
m <- matrix(0, nrow=n, ncol=n)
m[matrix(rep(seq_len(n), 2), ncol=2)] <- 1
m
}
Rdiag(4)
n <- 5e3
t1 <- system.time(d1 <- diag(n))
t2 <- system.time(d2 <- Rdiag(n))
all.equal(d1, d2)
rbind(diag=t1, Rdiag=t2, ratio=t1/t2)
Anyway, why don't you create it once, save a copy and use it many times?
Hope this helps,
Rui Barradas
Em 07-06-2012 08:55, Ceci Tam escreveu:
Hello, I am trying to build a large size identity matrix using
diag(). The
size is around 23000 and I've tried diag(23000), that took a long time.
Since I have to use this operation several times in my program, the
running
time is too long to be tolerable. Are there any alternative for diag(N)?
Thanks
Cheers,
yct
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