Sort rows in data table in decreasing order on string key order -x v gives error on data table 1 9 4 or earlier

Question

Let s say I have the following data table in R     library data table    DT   data table x rep c  b   a   c   each 3   y c 1 3 6   v 1 9    I want to order it by two columns  say columns x and v   I used this    DT order x v     sorts first by x then by v  both in ascending order    But now  I want to sort it by x  in decreasing order  and have the following code     DT order -x    Error in -x   invalid argument to unary operator   Therefore  I think this error is due to the fact that class DT x  character  Could you give me any suggestion in order to solve this issue   I know I can use DT order x decreasing TRUE    but I want to know the syntax to sort by several columns using both ways  some decreasing  some increasing  at the same time    Note that if you use DT order -y v   the result is ok  but if you use DT order -x v   there is an error  So  my question is  how to solve this error

User · Answer

DT order -x   works as expected  I have data table version 1 9 4  Maybe this was fixed in a recent version  Also  I suggest the setorder DT  -x  syntax in keeping with the set  commands like setnames  setkey

User · Answer

You can only use - on the numeric entries  so you can use decreasing and negate the ones you want in increasing order   DT order x -v decreasing TRUE          x y v   1   c 1 7   2   c 3 8   3   c 6 9   4   b 1 1   5   b 3 2   6   b 6 3   7   a 1 4   8   a 3 5   9   a 6 6

User · Answer

Update data table v1 9 6  now supports OP s original attempt and the following answer is no longer necessary   You can use DT order -rank x   y       x y v 1  c 1 7 2  c 3 8 3  c 6 9 4  b 1 1 5  b 3 2 6  b 6 3 7  a 1 4 8  a 3 5 9  a 6 6

[r] Sort rows in data.table in decreasing order on string key `order(-x,v)` gives error on data.table 1.9.4 or earlier

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