The Art of R Programming

Return Values

The return value of a function can be any R object. Although the return value is often a list, it could even be another function.

You can transmit a value back to the caller by explicitly calling return(). Without this call, the value of the last executed statement will be returned by default. For instance, consider the oddcount() example from Chapter 1:

> oddcount
function(x)  {
   k <- 0  # assign 0 to k
   for (n in x)  {
      if (n %% 2 == 1) k <- k+1  # %% is the modulo operator
   }
   return(k)
}

This function returns the count of odd numbers in the argument. We could slightly simplify the code by eliminating the call to return(). To do this, we evaluate the expression to be returned, k, as our last statement in the code:

oddcount <- function(x) ...