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<body class='hmmessage'><div dir='ltr'><p abp="4849">Hello to everyone,</p><p abp="4850"> </p><p abp="4851">Let's consider, just by way of example, the following date and data table:</p><p abp="4852"> </p><p abp="4853"><font face="Courier New,sans-serif" size="2" style="font-size: 10pt;" abp="4921">opening <- as.Date("1990-01-01")<br abp="4922">DT <- data.table(ID=c(1,2,3),<br abp="4923"> start=c("1985-01-01","1993-07-15","1993-05-17"),<br abp="4924"> end=c("1992-05-01","1997-02-25","2002-01-01"),<br abp="4925"> value=c(7.8, 3.2, 20.0))</font></p><p abp="4858"> </p><p abp="4859">FIRST QUESTION: </p><p abp="4859"> </p><p abp="4859">If I execute:</p><p abp="4859"> </p><p abp="4859"><font face="Courier New,sans-serif" size="2" style="font-size: 10pt;" abp="4926">DTNEW <- DT[ , { <br abp="4927"> if (all(start <= opening)){ <br abp="4928"> result <- list(start, end, t.dif= unclass(round(difftime(end, start)/365.25,1)), value) <br abp="4929"> } else { <br abp="4930"> result <- list(start, end, t.dif= 20, value)<br abp="4931"> } <br abp="4932"> result}, by=ID] </font></p><p abp="4859"><font face="Courier New" size="2"></font> </p><p abp="4859"><font face="Calibri" abp="4933">Why can I not keep the column names?</font></p><p abp="4859"><font face="Courier New,sans-serif" abp="4934"> ID t.dif <br abp="4935">1: 1 1985-01-01 1992-05-01 7.3 7.8<br abp="4936">2: 2 1993-07-15 1997-02-25 20.0 3.2<br abp="4937">3: 3 1993-05-17 2002-01-01 20.0 20.0</font><br abp="4938"></p><p abp="4859">SECOND QUESTION:</p><p abp="4859"> </p><p abp="4859">I would want to remove rows where <font face="Courier New,sans-serif">t.dif=value</font> in the final result. Then, I tried:</p><p abp="4859"> </p><p abp="4859"><font face="Courier New" size="2" abp="4939">DTNEW <- DT[ , { <br abp="4940"></font><font face="Courier New" size="2" abp="4941"> if (all(start <= opening)){ <br abp="4942"> result <- list(start, end, t.dif= unclass(round(difftime(end, start)/365.25,1)), value) <br abp="4943"> } else { <br abp="4944"> result <- list(start, end, t.dif= 20, value)<br abp="4945"> } <br abp="4946"> result[!(t.dif == value)]}, by=ID] </font></p><p abp="4859"> </p><p abp="4859">But R does not find the variable<font face="Courier New,sans-serif" abp="4947"> t.dif</font> !!</p><p abp="4859"> </p><p abp="4859">Thank you for your time to all of the members of the list!!</p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p><p abp="4859"> </p> </div></body>
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