R help - May 2009 - Problems with randomly generating samples

Dear R users,
Can anyone please tell me how to generate a large number of samples in R, given
certain distribution and size.
For example, if I want to generate 1000 samples of size n=100, with a N(0,1)
distribution, how should I proceed?
(Since I dont want to do "rnorm(100,0,1)" in R for 1000 times)
 
Thanks for help

Debbie


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> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org] On
> Behalf Of Debbie Zhang
> Sent: Wednesday, May 13, 2009 8:18 AM
> To: r-help at r-project.org
> Subject: [R] Problems with randomly generating samples
> 
> 
> Dear R users,
> Can anyone please tell me how to generate a large number of samples in R,
given
> certain distribution and size.
> For example, if I want to generate 1000 samples of size n=100, with a
N(0,1)
> distribution, how should I proceed?
> (Since I dont want to do "rnorm(100,0,1)" in R for 1000 times)
> 
> Thanks for help
> 
> Debbie
> 
> 
How about

samples <- rnorm(1000*100,0,1)
dim(samples) <- c(1000,100)

Hope this is helpful,

Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA  98504-5204

On 13-May-09 15:18:05, Debbie Zhang wrote:
> Dear R users,
> Can anyone please tell me how to generate a large number of samples in
> R, given certain distribution and size.
> For example, if I want to generate 1000 samples of size n=100, with a
> N(0,1) distribution, how should I proceed? 
> (Since I dont want to do "rnorm(100,0,1)" in R for 1000 times)
>  
> Thanks for help
> Debbie
One possibility is

  nsamples <- 1000
  sampsize <- 100
  Samples <- matrix(rnorm(nsamples*sampsize,0,1),nrow=nsamples)

Then each row of the matrix Samples will be a sample of size 'sampsize',
the i-th can be accessed as Samples[i,], and there are 'nsamples' rows
to choose from.

Ted.

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Date: 13-May-09                                       Time: 16:46:05
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