expression {base} | R Documentation |
Unevaluated Expressions
Usage
expression(...)
is.expression(expr)
as.expression(expr)
Value
An “expression” object containing its
unevaluated arguments. Expression objects conceptually are
lists of “calls” and so the subsetting operations which apply
to lists also apply to them. For compatibility with S,
the mode
function will return "expression"
for expression objects.
is.expression
returns TRUE
if expr is
an expression object and FALSE
otherwise.
as.expression
attempts to coerce its argument
into an expression object.
See Also
call
, eval
, function
.
Further,text
and legend
for plotting math
expressions.
Examples
length(ex1 <- expression(1+ 0:9))# 1
ex1
eval(ex1)# 1:10
length(ex3 <- expression(u,v, 1+ 0:9))# 3
mode(ex3 [3]) # expression
mode(ex3[[3]])# call
rm(ex3)