On Wed, Jan 20, 2010 at 4:37 PM, Dimitri Liakhovitski <ld7...@gmail.com> wrote:
> Hello!
>
> I have a data frame with a factor and a numeric variable:
>
> x<-data.frame(factor=c("b","b","d","d","e","e"),values=c(1,2,10,20,100,200))
>
> For each level of "factor" - I would like to divide each value of
> "values" by the mean of "values" that corresponds to the level of
> "factor"
> In other words, I would like to get a new variable that is equal to:
> 1/1.5
> 2/1.5
> 10/15
> 20/15
> 100/150
> 200/150
>
> I realize I could do it through tapply starting with:
> factor.level.means<-tapply(x$values,x$factor,mean) ... etc.
>
>
> But it seems clunky to me.
> Is there a more elegant way of doing it?Here's one way with the plyr package: library(plyr) ddply(x, "factor", transform, scaled = values / mean(values, na.rm = T)) Hadley -- http://had.co.nz/ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
