Accessing Arbitrary Columns from an R Data Frame using with()
- by johnmyleswhite
Suppose that I have a data frame with a column whose name is stored in a variable. Accessing this column using the variable is easy using bracket notation:
df <- data.frame(A = rep(1, 10), B = rep(2, 10))
column.name <- 'B'
df[,column.name]
But it is not obvious how to access an arbitrary column using a call to with(). The naive approach
with(df, column.name)
effectively evaluates column.name in the caller's environment. How can I delay evaluation sufficiently that with() will provide the same results that brackets give?
