Select / assign to data.table when variable names are stored in a character vector

Question

How do you refer to variables in a data.table if the variable names are stored in a character vector? For instance, this works for a data.frame:

Answer 1

You could try this

colname <- as.name("COL_NAME")

DT2 <- DT[, list(COL_SUM=sum(eval(colname, .SD))), by = c(group)]