Actual Arguments
Usage
substitute(expr, env=NULL)
quote(expr, env=NULL)
Description
substitute returns the expression which was typed
as the value of a formal argument.
quote is a synonym useful to lisp programmers.Details
The typical use of this is to create informative
labels for data sets and plots.
The myplot example below shows a simple use of this facility.
It uses the functions deparse and substitute
to create labels for a plot which are character string versions
of the actual arguments to the function myplot.See Also
missing for argument ``missingness''.Examples
substitute(expression(a + b), list(a = 1))#> expression(1 + b)
myplot <- function(x, y)
plot(x, y, xlab=deparse(substitute(x)),
ylab=deparse(substitute(y)))
## Simple examples about lazy evaluation, etc:
f1 <- function(x, y = x) { x <- x + 1; y }
s1 <- function(x, y = substitute(x)) { x <- x + 1; y }
s2 <- function(x, y) { if(missing(y)) y <- substitute(x); x <- x + 1; y }
a <- 10
f1(a)# 11
s1(a)# 11
s2(a)# a
typeof(s2(a))# "symbol"