R: Partial substitution in expressions

bquote {base}

R Documentation

Partial substitution in expressions

Description

An analogue of the LISP backquote macro. bquote quotes its argument except that terms wrapped in .() are evaluated in the specified where environment. If splice = TRUE then terms wrapped in ..() are evaluated and spliced into a call.

Usage

bquote(expr, where = parent.frame(), splice = FALSE)

Arguments

`expr`	A language object.
`where`	An environment.
`splice`	Logical; if `TRUE` splicing is enabled.

Value

A language object.

Examples

require(graphics)

a <- 2

bquote(a == a)
quote(a == a)

bquote(a == .(a))
substitute(a == A, list(A = a))

plot(1:10, a*(1:10), main = bquote(a == .(a)))

## to set a function default arg
default <- 1
bquote( function(x, y = .(default)) x+y )

exprs <- expression(x <- 1, y <- 2, x + y)
bquote(function() {..(exprs)}, splice = TRUE)