Using tapply to return multiple values as an array

complex_summary_w_tapply.R

data(warpbreaks)

my.summary <- function(vals) {
	return(c(avg=mean(vals),sd=sd(vals)))
}

sum.warpbreaks <- with(warpbreaks,tapply(breaks,list(tension,wool),my.summary))

sum.warpbreaks <- array(unlist(sum.warpbreaks),
	dim=c(length(sum.warpbreaks[1,1][[1]]),dim(sum.warpbreaks)),
	dimnames=c(summary=list(names(sum.warpbreaks[1,1][[1]])),
		dims=dimnames(sum.warpbreaks))
)

sum.warpbreaks