Hi,
system.time({
set.seed(111)
colSums(matrix(sample(c(-1, 1), 40*10000, TRUE), ncol = 10000))
})
user system elapsed
0.032 0.012 0.041
system.time({
set.seed(112)
list1<-vector("list",10000)
for(i in 1:10000){
list1[[i]]<-sample(c(-1,1),40,replace=TRUE)}
dat1<-do.call(rbind,lapply(list1,function(x) sum(x)))
dat2<-matrix(dat1,ncol=200,byrow=TRUE)
})
user system elapsed
0.112 0.000 0.111
#modified version
system.time({
set.seed(112)
list1<-vector("list",10000)
for(i in 1:10000){
list1[[i]]<-sample(c(-1,1),40,replace=TRUE)}
dat1<-unlist(lapply(list1,function(x) sum(x)))
})
user system elapsed
0.092 0.000 0.092
It seems like Michael's solution is better in terms of the CPU utilization. I
guess, the loop created the difference.
A.K.
----- Original Message -----
From: Michael Weylandt <michael.weyla...@gmail.com>
To: darnold <dwarnol...@suddenlink.net>
Cc: "r-help@r-project.org" <r-help@r-project.org>
Sent: Friday, August 3, 2012 10:20 PM
Subject: Re: [R] Head or Tails game
On Aug 3, 2012, at 9:14 PM, darnold <dwarnol...@suddenlink.net> wrote:
> David,
>
> set.seed(123) # always good to make reproducible
> winnings <- sum(sample(c(-1,1), 10000, replace=TRUE))
>
> Unfortunately, that's not the game. The game requires 40 flips of a coin.
>
> Then you have to play the game 10,000 times.
>
colSums(matrix(sample(c(-1, 1), 40*10000, TRUE), ncol = 10000))
or some such
Michael
> D.
>
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Head-or-Tails-game-tp4639142p4639145.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> 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
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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.
______________________________________________
R-help@r-project.org mailing list
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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.
