R help - Aug 2011 - How to store the output of a loop into a matrix??

Hello,

I want to create a matrix of N random numbers with a uniform distributions.
Later, I want to repeat T times each row of this matrix. For this I do the
following loop:

N<-45
T<-10
n<-N*T
a<-matrix(runif(N,min=-1,max=1),nr=N)

mymat<-matrix(rep(NA,n),nr=n,nc=1)
for(i in i:N){
b<-rep(a[i,],T)
mymat[i,]<-b
}

Mi problem is that with this loop I can see the output of the loop but I canot
get the matrix (mymat) that contains the full output of the loop.

Please, somebody know how can I create a matrix that contains the output of the
loop with a dimension NTx1 (450x1).

Thanks a lot for your help.
Alexandra

	[[alternative HTML version deleted]]

Hi Alexandra,

Here is an alternative without using a loop:

matrix(sapply(a, rep, T), ncol = 1)

HTH,
Jorge


On Wed, Aug 24, 2011 at 9:10 PM, Soberon Velez, Alexandra Pilar <> wrote:
> Hello,
>
> I want to create a matrix of N random numbers with a uniform distributions.
> Later, I want to repeat T times each row of this matrix. For this I do the
> following loop:
>
> N<-45
> T<-10
> n<-N*T
> a<-matrix(runif(N,min=-1,max=1),nr=N)
>
> mymat<-matrix(rep(NA,n),nr=n,nc=1)
> for(i in i:N){
> b<-rep(a[i,],T)
> mymat[i,]<-b
> }
>
> Mi problem is that with this loop I can see the output of the loop but I
> canot get the matrix (mymat) that contains the full output of the loop.
>
> Please, somebody know how can I create a matrix that contains the output of
> the loop with a dimension NTx1 (450x1).
>
> Thanks a lot for your help.
> Alexandra
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>
	[[alternative HTML version deleted]]

Hi:

It's straightforward to write a simple function to do this:

simmat <- function(N, t1) matrix(rep(runif(N, min = -1, max = 1), each
= t1), nrow = N, byrow = TRUE)
v <- simmat(45, 10)
head(v, 3)

HTH,
Dennis

PS: T is a reserved word in R (abbreviation for the logical TRUE) and
should not be used as a variable name; similarly, t is the name of a
very common function (for matrix transpose) so it shouldn't be used as
a variable name, either. This is why I chose t1 in the function above.

On Wed, Aug 24, 2011 at 6:10 PM, Soberon Velez, Alexandra Pilar
<alexandra.soberon at unican.es> wrote:
> Hello,
>
> I want to create a matrix of N random numbers with a uniform distributions.
Later, I want to repeat T times each row of this matrix. For this I do the
following loop:
>
> N<-45
> T<-10
> n<-N*T
> a<-matrix(runif(N,min=-1,max=1),nr=N)
>
> mymat<-matrix(rep(NA,n),nr=n,nc=1)
> for(i in i:N){
> b<-rep(a[i,],T)
> mymat[i,]<-b
> }
>
> Mi problem is that with this loop I can see the output of the loop but I
canot get the matrix (mymat) that contains the full output of the loop.
>
> Please, somebody know how can I create a matrix that contains the output of
the loop with a dimension NTx1 (450x1).
>
> Thanks a lot for your help.
> Alexandra
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.
>