[R] Loop removal?

[rijn@swi.psy.uva.nl]

Dear all,

I've got a quite large dataframe (stor) with rows subject and rt (reaction
time). I would like to split the reaction times per subject into 6 bins of
equal size. Right now, I'm using the following code:

bindata <- function(rt) {

  bindata <- rep(-1,length(rt))
  binwidth <- length(rt)/6

  bindata[order(rt)[(0*binwidth)+1:(1*binwidth)]] <- 1
  bindata[order(rt)[(1*binwidth)+1:(2*binwidth)]] <- 2
  bindata[order(rt)[(2*binwidth)+1:(3*binwidth)]] <- 3
  bindata[order(rt)[(3*binwidth)+1:(4*binwidth)]] <- 4
  bindata[order(rt)[(4*binwidth)+1:(5*binwidth)]] <- 5
  bindata[order(rt)[(5*binwidth)+1:(6*binwidth)]] <- 6

  bindata
}

for (i in unique(stor$subject)) {
  stor[stor$subject == i,]$bin <- bindata(stor[stor$subject == i,]$rt)
}

Although this code works fine, it does not "feel" very R'ish. Is there a
more elegant solution for this, especially one that removes the for-loop?

Thanks,
  Hedderik.

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