Stella Pachidi wrote:
Dear Erik and R experts,
Thank you for the fast response!
I include an example with the ChickWeight dataset:
ap.dat <- ChickWeight
matchMeanEx <- function(ind,dataTable,aggrTable)
{
index <- which((aggrTable[,1]==dataTable[["Diet"]][ind]) &
(aggrTable[,2]==dataTable[["Chick"]][ind]))
as.numeric(aggrTable[index,3])
}
avgW <- aggregate(ap.dat[["weight"]], by = list(ap.dat[["Diet"]],
ap.dat[["Chick"]]), FUN="mean")
meanW <- sapply((1:length(ap.dat[,1])), FUN=matchMeanEx, ap.dat, avgW)
ap.dat <- cbind (ap.dat, meanW)
How about simply using ave.
ap.dat$meanW <- ave(ap.dat$weight, list(ap.dat$Diet, ap.dat$Chick))
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