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<body class='hmmessage'><div dir='ltr'>Dear all,<BR>I'm working with a large database in wich I have some rows which have identical id and datep variables. Of these<br>duplicated rows, I only want to keep those row associated to the maximum value in marker variable. As an example:<BR>DT <- data.table(<br> id = rep(c(2,5),c(3,2)),<br> datep = as.Date(c('1995-04-20','1995-04-20', '1997-02-19', '1998-01-15','1998-01-15')),<br> marker = c(2,8,5,7,5),<br> group=rep(c("A","B"),c(3,2))<br> )<br>First, I sort by key variables: id, marker<br>DT[order(id,marker)]<BR> <BR>But afterwards I've tried different things and I'm not able to what I want:<br>DT[!duplicated(DT[c('id', 'datep')])]<br>DT[ !(duplicated %chin% c('id','datep'))]<br>DT[ !(duplicated %in% c('id','datep'))]<br>DT[,!(duplicated(DT[c("id","datep")])), by=list(id,datep)]<br>unique(DT[c('id','datep')])<BR>Please, does anyone know how to do it?<BR> </div></body>
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