Pass column name in data.table using variable [duplicate]
Solution 1:
Use the quote() and eval() functions to pass a variable to j. You don't need double-quotes on the column names when you do it this way, because the quote()-ed string will be evaluated inside the DT[]
temp <- quote(x)
DT[ , eval(temp)]
# [1] "b" "b" "b" "a" "a"
With a single column name, the result is a vector. If you want a data.table result, or several columns, use list form
temp <- quote(list(x, v))
DT[ , eval(temp)]
# x v
# 1: b 1.52566586
# 2: b 0.66057253
# 3: b -1.29654641
# 4: a -1.71998260
# 5: a 0.03159933