Thank you Eduard and Chris for your very rapid answers!!! Frank S. From: [email protected] Date: Tue, 25 Aug 2015 16:27:39 +0000 Subject: Re: [datatable-help] Conditional replacement using a single line To: [email protected]; [email protected] CC: [email protected]
You almost had it right with number 2: DT[,value:=ifelse(!duplicated(id),0,2)] On Tue, Aug 25, 2015 at 12:26 PM Eduard Antonyan <[email protected]> wrote: DT[, value := c(2, rep(0, .N-1)), by = id] On Tue, Aug 25, 2015 at 11:17 AM, Frank S. <[email protected]> wrote: Hello everyone, I ask a question directly linked with other question which I was answered in this list a year ago. Let the data table be: DT <- data.table(obs=1:7, id=c(1,1,1,4,4,4,4), time=c(3,4,7,5,8,10,15)) Now I add a new column, called "value", which contains all zeros except the first observation within each "id" group, which is equal to 2. One possible solution I was given is the following two code lines: > DT[ , value:=0] > DT[!duplicated(id), value:=2] But I wonder if it is possible to do the same ON A SINGLE CODE LINE. I have tried different options but they doesn't work: 1) DT[ , value:= c(0, 2), by=id] 2) DT[ , value:= ifelse( DT[!duplicated(id)]==T, 2, 0), by=id] Many thanks! _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
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