How to ==1 on a column defined by a variable

This is an extremely simple question, but again I'm confounded by the `data.table` syntax. If I have a string representing a column name -- such as `column <- "x"` -- how do I return just the rows that match a logical condition on that column? In a `data.frame`, if I wanted to return all rows of the table where column `x` equaled `1`, I'd write `df[df[,column] == 1,]`. How do I write that efficiently in a `data.table`? (Note, `dt[x == 1]` works fine, but not if you use a string like `column` representing the name of that column.) The answers here are close but do not seem to be enough to answer this question.