Message-ID: <f8e6ff050903301343j131dd194ye61a06623560271b@mail.gmail.com>
Date: 2009-03-30T20:43:55Z
From: Hadley Wickham
Subject: Calculating First Occurance by a factor
In-Reply-To: <37fda5350903301258u76a7bc35xebe38bb63828a130@mail.gmail.com>
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
--
http://had.co.nz/