[R] sum per day

[arun]

HI,
Try this:
library(plyr)
res<-ddply(myframe2,.(Timestamp=as.Date(myframe2$myframestime)),function(x) sum(x$Hunger))
 names(res)[2]<-"sumHunger"
 res[,1]<-format(res[,1],"%d.%m.%Y")
 res
#   Timestamp sumHunger
#1 24.09.2012         3
#2 25.09.2012         5
A.K.




----- Original Message -----
From: Tagmarie <Ramgad82 at gmx.net>
To: r-help at r-project.org
Cc: 
Sent: Tuesday, November 27, 2012 4:13 AM
Subject: [R] sum per day

Hello, 

I have a data frame somewhat like this one: 

myframe <- data.frame (Timestamp=c("24.09.2012 09:00", "24.09.2012 10:00",
"24.09.2012 11:00", 
                                   "25.09.2012 09:00", "25.09.2012 10:00",
"25.09.2012 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

Now I want to get the sum of "Hunger" for each day. In the end I want
something which looks like the following dataframe: 

myoutcome <- data.frame(Timestamp=c("24.09.2012", "25.09.2012"),
sumHunger=c(3, 5))

Does anyone know how to do that?
That would be very helpful and to all people who are willing to help me:
Thank you in advance! 

Best regards, 
Tagmarie 



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