Calculating group means
Jim: Did you forget about with() ? Instead of: by(lbtdat$latency,list(lbtdat$subject, lbtdat$condition,lbtdat$state),mean) ##do with(ibtdat,by(latency,list(subject,condition,state),mean)) Bert Gunter "Data is not information. Information is not knowledge. And knowledge is certainly not wisdom." H. Gilbert Welch
On Mon, Dec 23, 2013 at 6:37 PM, Jim Lemon <jim at bitwrit.com.au> wrote:
On 12/23/2013 11:31 PM, Laura Bethan Thomas [lbt1] wrote:
Hi All,
Sorry for what I imagine is quite a basic question. I have been trying to
do is create latency averages for each state (1-8) for each participant
(n=13) in each condition (1-10). I'm not sure what function I would need, or
what the most efficient ay of calculating this would be. If you have any
help with that I would be very grateful.
structure(list(subject = c(1L, 1L, 1L, 1L, 1L, 1L), conditionNo = c(1L,
1L, 1L, 1L, 1L, 1L), state = c(5L, 8L, 7L, 8L, 1L, 7L), latency = c(869L,
864L, 1004L, 801L, 611L, 679L)), .Names = c("subject", "conditionNo",
"state", "latency"), row.names = 3:8, class = "data.frame")
Hi Laura, You can do it like this: # make up enough data to do the calculation lbtdat<-data.frame(subject=rep(1:13,each=160), condition=rep(rep(rep(1:10,each=8),2),13), state=rep(rep(1:8,20),13), latency=sample(600:1100,2080,TRUE)) by(lbtdat$latency,list(lbtdat$subject, lbtdat$condition,lbtdat$state),mean) but you are going to get a rather long list of means. Jim
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