Hi Arun, First of all, thnak you for answering once again! Following your suggestion, I've tried to wrap my j-expression: > unique(DT[ , print(visit <- > as.Date(c(paste0(year(start[1]):(year(end[1])-1),"-12-31")))),by=id]) # [1] "2007-12-31" "2008-12-31" # [1] "2010-12-31" "2011-12-31" # Empty data.table (0 rows) of 1 col: id But i do not have any idea which the problem is. Please, can you give me any additional help? Subject: Re: [datatable-help] Avoid warnings when obtaining fictitious rows From: [email protected] Date: Fri, 28 Aug 2015 11:55:27 +0200 CC: [email protected] To: [email protected]
Wrap the j-exp with print. It will help you identify what the issue is. Arun On 27 Aug 2015, at 13:58, Frank S. <[email protected]> wrote: Hello everyone, I can execute my R code but I obtain a warning message and I do not know how to avoid it. Let's consider, just by way of example, the following data table with 2 subjects under study: DT <- data.table(id=c(2,2,2,11,11), start=c(rep(as.Date("2007-01-01"),3),rep(as.Date("2010-09-30"),2)), visit=c("2007-03-01","2008-07-15","2008-11-17","2010-10-15","2011-05-17"), end=c(rep(as.Date("2009-05-01"),3),rep(as.Date("2012-03-25"),2))) I get a new data table which assigns a fictitious visit on each 31 December between the dates "start" and "end" corresponding to each individual: DT.new <- unique(DT[,list(start, visit=as.Date(c(paste0(year(start[1]):(year(end[1])-1),"-12-31"))), end), by=id]) Warning messages: In `[.data.table`(DT, , list(start, visit = as.Date(c(paste0(year(start[1]):(year(end[1]) - : Column 2 of result for group 1 is length 2 but the longest column in this result is 3. Recycled leaving remainder of 1 items. This warning is once only for the first group with this issue. The R code works, but how can I avoid the warning? Many thanks for any suggestion!! _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
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