I would suggest using summaryBy()

library(doBy)
# sample data with you specifications
subject <- as.factor(rep(seq(13), each = 5))
state <- as.factor(sample(c(1:8), 65, replace = TRUE))
condition <- as.factor(sample(c(1:10), 65, replace = TRUE))
latency <- runif(65, min=750, max = 1100)

dat <- data.frame(subject, state, condition, latency)

summaryBy(latency~subject+state+condition, data = dat, FUN = function(x)
mean(x))

Regards,


On Mon, Dec 23, 2013 at 6:31 AM, Laura Bethan Thomas [lbt1] <lbt1@aber.ac.uk
> 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")
> >
> > Thanks again,
> >
> > Laura
>
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>



-- 
Charles Determan
Integrated Biosciences PhD Candidate
University of Minnesota

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