Subset data.table by logical column

Question

I have a data.table with a logical column. Why the name of the logical column can not be used directly for the i argument? See the example.

Answer 1

From ?data.table

Advanced: When i is a single variable name, it is not considered an expression of column names and is instead evaluated in calling scope.

So dt[x] will try to evaluate x in the calling scope (in this case the global environment)

You can get around this by using ( or { or force

dt[(x)]
dt[{x}]
dt[force(x)]