R help - Feb 2012 - generate matrices

Dear all,
I would like to generate 500 matrices of 20 numbers from
standard normal distribution with names x1,x2,x3,….x500.  
I tried with loop for, but I don’t know how to name matices :
for (i in 1:500)  {
   x[[i]] <- matrix(rnorm(20), 4)     }
Any suggestion?
Thanks,  Blaž
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What about this?

B <- 500
X <- matrix(rnorm(B*20), ncol = B)
colnames(X) <- paste('x', 1:B, sep = "")
head(X)

Thus, each column correspond to a sample of 20 numbers from a standard
normal distribution.

HTH,
Jorge.-


On Thu, Feb 9, 2012 at 8:38 AM, Blaz Simcic <> wrote:
> Dear all,
> I would like to generate 500 matrices of 20 numbers from
> standard normal distribution with names x1,x2,x3,….x500.
> I tried with loop for, but I don’t know how to name matices :
> for (i in 1:500)  {
>    x[[i]] <- matrix(rnorm(20), 4)     }
> Any suggestion?
> Thanks,  Blaž
>        [[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]]

On Feb 9, 2012, at 8:38 AM, Blaz Simcic wrote:
> Dear all,
> I would like to generate 500 matrices of 20 numbers from
> standard normal distribution with names x1,x2,x3,?.x500.
> I tried with loop for, but I don?t know how to name matices :
> for (i in 1:500)  {
>    x[[i]] <- matrix(rnorm(20), 4)     }
> Any suggestion?
Don't do it that way. Create an array-object instead.

 > x <- array(NA, dim=c(4,5,500) )
 > x[] <- rnorm(4*5*500)
 > str(x)
  num [1:4, 1:5, 1:500] -0.721 0.896 -1.432 0.386 -1.111 ...
 > dimnames(x)[[3]] <- paste("x", 1:500, sep="")
 > str(x)
  num [1:4, 1:5, 1:500] -0.721 0.896 -1.432 0.386 -1.111 ...
  - attr(*, "dimnames")=List of 3
   ..$ : NULL
   ..$ : NULL
   ..$ : chr [1:500] "x1" "x2" "x3" "x4"
...

-- 
David Winsemius, MD
West Hartford, CT