Or using ddply from plyr,
library(plyr)
myframe <- data.frame (ID=c("Ernie", "Ernie", "Ernie", "Bert", "Bert",
"Bert"), Timestamp=c("24.09.2012 09:00", "24.09.2012 10:00", "24.09.2012
11:00"), Hunger=c(1,1,1,2,2,1) )
myframe
myframestime <- as.POSIXct (strptime(as.character(myframe$Timestamp),
"%d.%m.%Y %H:%M"), tz="GMT")
myframestime
myframe2 <- cbind (myframe,myframestime)
myframe2
ddply(myframe2,.(ID),summarise,Last2=mean(tail(Hunger,2)))
Felipe D. Carrillo
Supervisory Fishery Biologist
Department of the Interior
US Fish & Wildlife Service
California, USA
http://www.fws.gov/redbluff/rbdd_jsmp.aspx
From: Tagmarie <ramga...@gmx.net>
>To: r-help@r-project.org
>Sent: Thursday, October 25, 2012 7:35 AM
>Subject: [R] mean of a value of the last 2 hours
>
>Hello,
>I have a data frame somewhat like that:
>
>myframe <- data.frame (ID=c("Ernie", "Ernie", "Ernie", "Bert", "Bert",
>"Bert"), Timestamp=c("24.09.2012 09:00", "24.09.2012 10:00", "24.09.2012
>11:00"), Hunger=c(1,1,1,2,2,1) )
>myframestime <- as.POSIXct (strptime(as.character(myframe$Timestamp),
>"%d.%m.%Y %H:%M"), tz="GMT")
>myframe2 <- cbind (myframe,myframestime)
>myframe2$Timestamp <- NULL
>myframe2
>
>I want to add an additional column at the right and get in each row a value
>which shows the mean of "hunger" of the last two hours.
>
>Does anyone know how that works? That would be very helpful.
>
>
>
>--
>View this message in context:
>http://r.789695.n4.nabble.com/mean-of-a-value-of-the-last-2-hours-tp4647415.html
>Sent from the R help mailing list archive at Nabble.com.
>
>______________________________________________
>R-help@r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
>
>
>
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