[R] Simple operation on a subset of data

Dimitris Rizopoulos dimitris.rizopoulos at med.kuleuven.ac.be
Fri Nov 12 13:30:46 CET 2004

Hi Giacomo,

"An Introduction to R" is very useful document for all these things! 
Look at ?subset and try:

dat <- data.frame(x=sample(1:2, 10, TRUE), y=sample(c(4,5), 10, TRUE), 
summary(subset(dat, x==1 & y==4, select=z))

I hope it helps.


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

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/396887
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat

----- Original Message ----- 
From: "Giacomo De Giorgi " <uctpgde at ucl.ac.uk>
To: <r-help at stat.math.ethz.ch>
Sent: Friday, November 12, 2004 1:04 PM
Subject: [R] Simple operation on a subset of data

> Sorry for the silly question.
> I am trying to perform a simple operation on a subsample of my data
> loaded as data and attached:
> data<-read.dta(name file)
> attach(data)
> Say x=1,2 and y=4,5 I want to summarize z only if x=1 & y=4. I 
> thought
> that the way to do that would be to
> write if((x=1) & (y=4)) summary(z)
> butwhen I do this the result I get is for the whole data 
> (irrespective
> of the conditions imposed). Can anyone help?
> Thanks
> Giacomo
> [[alternative HTML version deleted]]
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