[R] Averaging rows if a condition is true.

[Mohamed Lajnef]

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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>   


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