Here is an example of an approach:
> 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"),
+ Speed=c(1,1,2,5,1,6))
> myframestime <- as.POSIXct (strptime(as.character(myframe$Timestamp),
+ "%d.%m.%Y %H:%M"), tz="GMT")
> myframe2 <- cbind (myframe,myframestime)
> myframe2$Timestamp <- NULL
> myframe2
Speed myframestime
1 1 2012-09-24 09:00:00
2 1 2012-09-24 10:00:00
3 2 2012-09-24 11:00:00
4 5 2012-09-25 09:00:00
5 1 2012-09-25 10:00:00
6 6 2012-09-25 11:00:00
>
> # split the dataframe into "days' and then find average of Speed (for example)
> tapply(myframe2$Speed, cut(myframe2$myframestime, 'day'), mean)
2012-09-24 2012-09-25
1.333333 4.000000
>
>
On Tue, Nov 27, 2012 at 9:02 AM, Tagmarie <ramga...@gmx.net> wrote:
> Hello,
> I tried to construct my very first loop today and completly failed :-(
> Maybe someone can help me?
> I have a dataframe 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"),
> Speed=c(1,1,2,5,1,6))
> 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 construct a loop for every day, i.e. for each day I want to do
> some calculations.
> (I know in the example it would be easier to do it differently, my real data
> are little more complex).
>
> And BTW: Thanks for helping me earlier today with that other problem :-)
>
>
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/loop-with-date-tp4650961.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.
--
Jim Holtman
Data Munger Guru
What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.
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