TITLE(missing @@ Does a Formal Argument have a Value?)
USAGE(missing(x))
ALIAS(missing)
DESCRIPTION(
LANG(missing) can be used to test whether a value was specified
as an argument to a function.
The following example shows how a plotting function
can be written to work with either a pair of vectors
giving x and y coordinates of points to be plotted
or a single vector giving y values to be plotted
against their indexes.
)
EXAMPLES(
myplot <- function(x,y) {
                if(missing(y)) {
                        y <- x
                        x <- 1:length(y)
                }
                plot(x,y)
        }
)
