R help - Sep 2005 - R: extracting elements in a matrix

Dear R-users
 
For a given matrix of dimension, say (n,p), I'd like to extract for every
column those elements that are bigger than twice the interquartile range of
the corresponding column. 
 
Can I get these elements without using a loop?
 
 
Thank you for your help
 
 
Frank
 
 
 

		
	
 

	[[alternative HTML version deleted]]

you could try this:

mat <- matrix(rnorm(100 * 10), 100, 10)

ind <- apply(mat, 2, function(x){
    iqr <- diff(quantile(x, probs = c(0.25, 0.75)))
    x[x > 2 * iqr]
})


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Frank Schmid" <frank.schmid at vwi.unibe.ch>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, September 22, 2005 11:23 AM
Subject: [R] R: extracting elements in a matrix

> Dear R-users
>
> For a given matrix of dimension, say (n,p), I'd like to extract for 
> every
> column those elements that are bigger than twice the interquartile 
> range of
> the corresponding column.
>
> Can I get these elements without using a loop?
>
>
> Thank you for your help
>
>
> Frank
>
>
>
>
>
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

... you can, for example

set.seed(13)
x<-matrix(rnorm(100),20,5)
lapply(split(x,col(x)),
       function(x){
         limit<-diff(quantile(x,c(.25,.75)))
         x[x>limit]
       })
output:
$"1"
[1] 1.775163 1.142526 1.229507 1.105144 1.396432
$"2"
[1] 1.836163
$"3"
[1] 1.590034 1.614479 1.408354 1.483691
$"4"
[1] 1.745427
$"5"
[1] 1.602120

Peter Wolf

Frank Schmid wrote:
>Dear R-users
> 
>For a given matrix of dimension, say (n,p), I'd like to extract for
every
>column those elements that are bigger than twice the interquartile range of
>the corresponding column. 
> 
>Can I get these elements without using a loop?
> 
> 
>Thank you for your help
> 
> 
>Frank
> 
> 
> 
>
>		
>	
> 
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>