This should do it:
> x <- read.table(textConnection("Date time value
+ 20110620 11:18:00 7
+ 20110620 11:39:00 9
+ 20110621 11:41:00 8
+ 20110621 11:40:00 6
+ 20110622 14:05:00 8
+ 20110622 14:06:00 6"), header=TRUE, as.is=TRUE)
>
> x$time <- as.POSIXct(strptime(x$time, "%H:%M:%S"))
> do.call(rbind, lapply(split(x, x$Date), function(.day){
+ .day[which.max(.day$time),]
+ }))
Date time value
20110620 20110620 2008-01-10 11:39:00 9
20110621 20110621 2008-01-10 11:41:00 8
20110622 20110622 2008-01-10 14:06:00 6
>
On Jan 10, 2008 5:36 PM, Kondamani, Arjun (GMI - NY Corporate Bonds)
<[EMAIL PROTECTED]> wrote:
> I have a dataframe as follows:
>
> Date time value
> 20110620 11:18:00 7
> 20110620 11:39:00 9
> 20110621 11:41:00 8
> 20110621 11:40:00 6
> 20110622 14:05:00 8
> 20110622 14:06:00 6
>
> For every date, I want to extract the row that has the greatest time.
> Therefore, ending up like:
> 20110620 11:39:00 9
> 20110621 11:41:00 8
> 20110622 14:07:00 6
>
> I am using for loops (for every date, find largest time value) to do
> this determination, but I am sure there is a simpler way in "R". Has
> anyone run into this before?
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--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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