Re: Generating a vector dynamically

[David L Lorenz <lorenz@usgs.gov>]

Hi,
  It is probably a little more
efficient to take all of the samples and then process them. So another
way:

res <- colSums(matrix(sample(d$x,
10*1000, rep=T), ncol=1000))

Dave

Tony Plate <tplate@blackmesacapital.com>
Sent by: s-news-owner@lists.biostat.wustl.edu

04/20/2006 07:13 PM

To	"Khan, Sohail" <khan@cshl.edu>
cc	s-news@lists.biostat.wustl.edu
Subject	Re: [S] Generating a vector dynamically

Here's one way to do what I think you want:

 > set.seed(1)
 > # Generate a sample data frame with one column 'x'
 > d <- data.frame(x=sample(c(10:14,100),50,rep=T))
 > # Create a vector with the sum of 1000 samples of size
 > # 10 (with replacement)
 > res <- sapply(1:1000, function(i) sum(sample(d$x, 10, rep=T)))
 > hist(res)
 >

Khan, Sohail wrote:
> Dear List
> 
> I want to write a "little" piece of  code which would
:
> 
> -- take sample of 10 values (randomly) from a data.frame column
> -- sum these values
> -- put the values in a vector
> -- repeat 1000 times
> 
> I would later draw a histogram of this generated vector.
> Thanks in advance for any advice/suggestions.
> 
> Sohail Khan
> Scientific Programmer
> COLD SPRING HARBOR LABORATORY
> Genome Research Center
> 500 Sunnyside Boulevard
> Woodbury, NY 11797
> (516)422-4076
> 
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