[R] Averaging rows if a condition is true.

[A Ezhil]

Thanks a lot, Mohamed. 

Kind regards,
Ezhil

--- On Mon, 9/7/09, Mohamed Lajnef <Mohamed.lajnef at inserm.fr> wrote:

> From: Mohamed Lajnef <Mohamed.lajnef at inserm.fr>
> Subject: Re: [R] Averaging rows if a condition is true.
> To: "A Ezhil" <ezhil02 at yahoo.com>
> Cc: r-help at r-project.org
> Date: Monday, September 7, 2009, 9:22 PM
> Hi,
> 
> Try to use aggregate function
> RSiteSearch ("aggregate")   #for help
> 
> 
> Regards
> ML
> 
> A Ezhil a écrit :
> > Dear All,
> >
> > I have matrix (50000 X 60) of subjects and their
> responses to a set of questions. All responses are
> classified into categories (500). I would like to average
> all subject's responses for each category. I wrote a code
> using a for loop but is not working. Could please tell me
> what's wrong with the code? I guess, there is a elegant R
> way of doing the same thing.
> >
> > Thanks in advance.
> >
> > Kind regards,
> > Ezhil
> >
> >
> > j <- 1; n <- dim(dat)[1]; cat <-
> as.character(dat[,1]);
> > row <- matrix(nrow=nrow(dat), ncol=ncol(dat));
> > for(i in 1:n-1) {
> >   if(cat[i] != cat[i+1]) {row[j, ]
> <- dat[j, ]}
> >   else {
> >       start <- j;
> >       end <- i;
> >       }
> >       row[j, ] <-
> colMeans(dat[j:i, ]);
> >       j+1;
> >   }
> >
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> reproducible code.
> >
> >   
> 
> 
> -- 
> Mohamed Lajnef
> INSERM Unité 955. 
> 40 rue de Mesly. 94000 Créteil.
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> 
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>