[R] average environmental data if AnimalID and Time is duplicated

[Jim Lemon]

On 09/26/2012 08:53 PM, Tagmarie wrote:
> Hello,
> I tried for about three hours now to solve this problem but I can't figure
> it out. I am sure someone knows how do it. At least I hope so.
>
> I have a data frame somewhat like this:
>
> myframe<- data.frame (ID=c("Ernie", "Ernie", "Bert", "Bert"),
> Timestamp=c("24.09.2012 09:00", "24.09.2012 09:00", "24.09.2012 10:00",
> "25.09.2012 10:00"), Hunger=c("1","5","2","2"), Temp=c("25","30","27","28")
> )
> myframe
>
> As you can see for Ernie I do have different data for 24.09.2012 9:00. Now I
> would like to average the Hunger and Temp value for this timestamp to get a
> data frame without duplicated Times and the respective average Temp and
> Hunger.
>
> I tried something like
> Meanframe<-  by(myframe[, 3:4], duplicated(myframe$ID,
> Zusatzdaten3$Timestamp) == TRUE, mean)
> but it doesn't work and I guess that it is also totally crap ;-)
>
Hi Tagmarie,
Your problem is that both Hunger and Temp are read in as factors. If you 
try it like this:

by(as.numeric(as.character(myframe[,3])),myframe[,"ID"],mean)
by(as.numeric(as.character(myframe[,4])),myframe[,"ID"],mean)

You might get what you want. The "as.character" call is necessary, 
otherwise you will get the wrong mean values.

Jim