Hi Val, Your problem is keeping the orders straight. You want dates decreasing and names increasing:
DF1<-read.table(text="name ddate A 2019-10-28 A 2018-01-25 A 2020-01-12 A 2017-10-20 B 2020-11-20 B 2019-10-20 B 2017-05-20 B 2020-01-20 C 2009-10-01 ",header=TRUE) DF1$Time<-as.POSIXct(DF1$ddate , format = "%Y-%m-%d") # get dates in decreasing order DF2<-DF1[order(DF1$Time,decreasing=TRUE),] # create the final output with the names in increasing order DF3<-data.frame(name=sort(unique(DF2$name))) # create a function that returns the first diff of a vector getdate1diff<-function(x) return(ifelse(length(x)>1,abs(diff(x))[1],0)) # apply the function by the unique names in DF2 DF3$date1diff<-by(DF2$Time,DF2$name,getdate1diff) DF3 Jim On Fri, May 15, 2020 at 1:00 PM Val <valkr...@gmail.com> wrote: > > HI All, > I have a sample of data frame > DF1<-read.table(text="name ddate > A 2019-10-28 > A 2018-01-25 > A 2020-01-12 > A 2017-10-20 > B 2020-11-20 > B 2019-10-20 > B 2017-05-20 > B 2020-01-20 > c 2009-10-01 ",header=TRUE) > > 1. I want sort by name and ddate on decreasing order and the output > should like as follow > A 2020-01-12 > A 2019-01-12 > A 2018-01-25 > A 2017-10-20 > B 2020-11-21 > B 2020-11-01 > B 2019-10-20 > B 2017-05-20 > c 2009-10-01 > > 2. Take the top two rows by group( names) and the out put should like > A 2020-01-12 > A 2019-01-12 > B 2020-11-21 > B 2020-11-01 > c 2009-10-01 > > 3. Within each group (name) get the date difference between the > first and second rows dates. If a group has only one row then the > difference should be 0 > > The final out put is > Name diff > A 365 > B 20 > C 0 > > Here is my attempt and have an issue at the sorting > DF1$DTime <- as.POSIXct(DF1$ddate , format = "%Y-%m-%d") > DF2 <- DF1[order(DF1$name, ((as.Date(DF1$DTime, decreasing = TRUE)))), ] > > not working > Any help? > > Thank you > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.
