subsetting dynamically -- subsetting by a variable that is defined in a function

Question

v1 = c(1,2,3)
v2 = c("a","b",NA)
X = data.frame(v1,v2)

f = function(X,d){
    subset(X,is.na(d)==0)
    }
f(X,"v2")

How can I get the subset of X for which any given column (inputted into the argument of a function) isn't missing?

Answer 1

Note: The function subset should not be used in functions but interactively only (see here).

f <- function(X, d) {
  X[!is.na(X[d]), ]
}

> f(X,"v2")
  v1 v2
1  1  a
2  2  b