[R] Loop removal?

rijn@swi.psy.uva.nl rijn at swi.psy.uva.nl
Mon Jul 31 15:52:37 CEST 2000


thanks to all who responded to my question. The various responses teached
me, again, a lot about R and the different philosophy of R compared to
programming languages. Especially the reply of Peter Malewski using the
tapply/unlist/rep functions was very insightful, and helped me to solve my

To explain why I needed this all: in a lexical decision (psychonomy)
experiment, the subjects had to respond at several predefined lags.
However, the response times show quite some variation, so besides an
analysis based on the 6 predefined lags, we also wanted to do an analysis
based on 6 groups each containing 1/6th of the fastest, slowest, etc RTs
per subject.

So, in the orginial dataframe, we had the columns subject, lag and rt, and
the code I posted in my last message was meant to add the column binlag.

subject  lag   rt     binlag
1        1     350    1
1        1     450    2
1        2     425    1 
1        2     475    2
2        1     425    1    
2        1     450    1
2        2     490    2
2        2     480    2

Sorry if I was unclear in my previous postings. Again, thanks for all the

P.S. The code I use now, is:

  bin.index <- function(data,bins=2) {
    # Code from Peter Malewski, added the sort command.
  stor <- stor[order(stor$subject,stor$rt),]
  stor$binlag <- unlist(tapply(stor$rt,stor$subject,bin.index,bins=6))

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