expression               package:base               R Documentation

Unevaluated Expressions

Description:

     Creates or tests for objects of mode `"expression"'.

Usage:

     expression(...)

     is.expression(x)
     as.expression(x, ...)

Arguments:

     ...: valid R expressions.

       x: an arbitrary R object.

Value:

     `expression' returns a vector of mode `"expression"' containing
     its arguments as unevaluated ``calls''.

     `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)

