Invalid argument to unary operator (on character column)-CodePudding

Say I have the below df

df <- data.table(group_id = c(1,1,2,2)
                 , week_no = c('2019-01', '2019-02', '2019-03', '2019-04')
                 ); df

   group_id week_no
1:        1 2019-01
2:        1 2019-02
3:        2 2019-03
4:        2 2019-04

And a grouped frank works fine:

df[, dummy := frankv(week_no), group_id]; df

   group_id week_no dummy
1:        1 2019-01     1
2:        1 2019-02     2
3:        2 2019-03     1
4:        2 2019-04     2

However, if I wanted to rank in descending order:

df[, dummy := frankv(-date), group_id]; df

I get the error:

Error in -date : invalid argument to unary operator

I suppose it is to do with column week_no's class being character. Is there a way around this other than ranking date in ascending order, then ranking the dummy column in descending order? Thank you.

CodePudding user response：

Is this what you are looking for?

library(data.table)

df[, dummy := frankv(week_no, order = -1L), group_id][]
#>    group_id week_no dummy
#> 1:        1 2019-01     2
#> 2:        1 2019-02     1
#> 3:        2 2019-03     2
#> 4:        2 2019-04     1

^{Created on 2021-10-25 by the reprex package (v0.3.0)}