Calculating First Occurance by a factor
On Mon, Mar 30, 2009 at 2:58 PM, Mike Lawrence <Mike.Lawrence at dal.ca> wrote:
I discovered Hadley Wickham's "plyr" package last week and have found
it very useful in circumstances like this:
library(plyr)
firstfixtime = ddply(
? ? ? .data = data
? ? ? , .variables = c('Sub','Tr','IA')
? ? ? , .fun <- function(df){
? ? ? ? ? ? ? df$FixTime[which.min(df$FixInx)]
? ? ? }
)
Or to save a little typing: ddply(data, .(Sub, Tr, IA), colwise(min, .(FixTime)) Hadley