Here is a slight variation of ones you have already received. This
also uses zoo.
In the DF<- line we read it in as a data frame. In the z<- line we convert
it to zoo using chron date/times (see R News 4/1 for more).
We calculate the positions of duplicate dates and in the last line we
extract the rows corresponding to non-duplicates.
Lines <- "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
"
library(zoo)
library(chron)
DF <- read.table(textConnection(Lines), header = TRUE, as.is = TRUE)
z <- zoo(DF$value, chron(unclass(as.Date(format(DF$Date), "%Y%m%d"))), DF$time)
isdup <- duplicated(dates(time(z)), fromLast = TRUE)
z[!isdup,]
For more on zoo see:
library(zoo)
vignette("zoo")
vignette("zoo-quickref")
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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