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<body class='hmmessage'><div dir='ltr'>Hi Arun,<BR> <BR>First of all, thnak you for answering once again!<BR> <BR>Following your suggestion, I've tried to wrap my j-expression:<BR> <BR>> unique(DT[ , print(visit <- as.Date(c(paste0(year(start[1]):(year(end[1])-1),"-12-31")))),by=id])<BR># [1] "2007-12-31" "2008-12-31"<BR># [1] "2010-12-31" "2011-12-31"<br># Empty data.table (0 rows) of 1 col: id<br> <BR>But i do not have any idea which the problem is.<BR> <BR>Please, can you give me any additional help?<BR> <BR><div><hr id="stopSpelling">Subject: Re: [datatable-help] Avoid warnings when obtaining fictitious rows<br>From: aragorn168b@gmail.com<br>Date: Fri, 28 Aug 2015 11:55:27 +0200<br>CC: datatable-help@lists.r-forge.r-project.org<br>To: f_j_rod@hotmail.com<br><br><div>Wrap the j-exp with print. It will help you identify what the issue is.<br><br>Arun</div><div><br>On 27 Aug 2015, at 13:58, Frank S. <<a href="mailto:f_j_rod@hotmail.com">f_j_rod@hotmail.com</a>> wrote:<br><br></div><blockquote><div>
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<div dir="ltr">Hello everyone,<br> <br>I can execute my R code but I obtain a warning message and I do not know how to avoid it.<br>Let's consider, just by way of example, the following data table with 2 subjects under study:<br> <br>DT <- data.table(id=c(2,2,2,11,11),<br> start=c(rep(as.Date("2007-01-01"),3),rep(as.Date("2010-09-30"),2)),<br> visit=c("2007-03-01","2008-07-15","2008-11-17","2010-10-15","2011-05-17"),<br> end=c(rep(as.Date("2009-05-01"),3),rep(as.Date("2012-03-25"),2)))<br> <br>I get a new data table which assigns a fictitious visit on each 31 December between<br>the dates "start" and "end" corresponding to each individual:<br> <br>DT.new <- unique(DT[,list(start,<br> visit=as.Date(c(paste0(year(start[1]):(year(end[1])-1),"-12-31"))), <br> end), by=id])<br> <br>Warning messages:<br>In `[.data.table`(DT, , list(start, visit = as.Date(c(paste0(year(start[1]):(year(end[1]) - :<br> 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.<br> <br>The R code works, but how can I avoid the warning?<br> <br>Many thanks for any suggestion!!<br> </div>
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