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generate matrices
4 messages · Blaz Simcic, Jorge I Velez, David Winsemius +1 more
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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
Inline below. -- Bert
On Thu, Feb 9, 2012 at 8:59 AM, David Winsemius <dwinsemius at comcast.net> wrote:
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)
Inefficient. Do it in one go: x <- array(rnorm(20*500), dim = c(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
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Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm