data.table: using setkey with a column name variable

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 which_id ?

This is what I've tried

 > eval( paste( 'setkey(W,' , which_id , ')' ) )
[1] "setkey(W, customer_id_A )"

But a call to tables() shows that the customer_id_A key didn't take.

 > evalq( paste( 'setkey(W,' , which_id , ')' ) )
[1] "setkey(W, customer_id_A )"

customer_id_A key still didn't take.

 > setkeyv( W , cols=which_id )


 > setkeyv( W , cols=c( which_id ) )

--> same thing, customer_id_A key isn't there.

Any pointers? Thanks.


setkeyv should work. Here is a reproducible example:

> library(data.table)
data.table 1.8.8  For help type: help("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

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