data.table: using setkey with a column name variable

Question

I have a variable name saved into the string variable which_id.

W is a data.table. How do I call setkey on W with

Answer 1

setkeyv should work. Here is a reproducible example:

library(data.table)
W <- data.table(customer_id_A = 1:2)
which_id <- "customer_id_A"
setkeyv(W, which_id)
tables()
##      NAME NROW MB COLS          KEY          
## [1,] W       2 1  customer_id_A customer_id_A
## Total: 1MB