Here are three possibilities: # 1 DF[!duplicated(DF$Datetime), ]
# 2 aggregate(DF[-1], DF[1], head, 1) These give the first one but if you want the last one use the fromLast= arg of duplicated or tail instead of head with aggregate. # 3 # The zoo package can read in data, convert the # first column to datetime and remove # duplicates via aggregation all at once: Lines <- 'Datetime,Temperature 2008-6-1 00:00:00,5 2008-6-1 02:00:00,5 2008-6-1 03:00:00,6 2008-6-1 03:00:00,0 2008-6-1 04:00:00,6 2008-6-1 04:00:00,0 2008-6-1 05:00:00,7 2008-6-1 06:00:00,7 ' library(zoo) library(chron) # z <- read.zoo("myfile.csv", sep = ",", header = TRUE, FUN = as.chron, # aggregate = function(x) head(x, 1)) z <- read.zoo(textConnection(Lines), sep = ",", header = TRUE, FUN = as.chron, aggregate = function(x) head(x, 1)) # or use tz = "" in place of FUN=as.chron if you want POSIXct. # See the three zoo vignettes and on dates and times see R News 4/1. On Sun, Nov 16, 2008 at 1:10 PM, Antje Nöthlich <[EMAIL PROTECTED]> wrote: > Hei R Users, > > i have the following dataframe: > > Datetime Temperature and many more > collumns > 1 2008-6-1 00:00:00 5 > 2 2008-6-1 02:00:00 5 > 3 2008-6-1 03:00:00 6 > 4 2008-6-1 03:00:00 0 > 5 2008-6-1 04:00:00 6 > 6 2008-6-1 04:00:00 0 > 7 2008-6-1 05:00:00 7 > 8 2008-6-1 06:00:00 7 > . . . > . . . > . . . > 3000 2008-8-31 00:00:00 3 > > > the problem is that row 3 & 4 and row 5 & 6 have the same "Datetime" value > but they differ in the values of the "Temperature" column. > Now for the whole dataframe i would like to delete rows that have the same > "Datetime" value as the prior row. > I have tried unique(dataframe), but it does not work here because the rows > are no real duplicates of each other. > thanks in advance for your help! > > Antje > > ______________________________________________ > 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. > ______________________________________________ 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.