exists {base}

R Documentation

Is a Variable Defined?

Description

This function looks to see if the name x has a value bound to it. If inherits is TRUE and a value is not found for x, then the parent frames of envir are searched until the name x is encountered. If mode is specified then only objects of that mode are sought. The function returns TRUE if the variable is encountered and FALSE if not.

Usage

exists(x, where =NULL, envir=sys.frame(sys.parent()), frame =NULL,
       mode = "any", inherits = TRUE)

Arguments

x	a variable name (given as a quoted string).
where, envir, frame	an environent to be searched. By default this is the environment where the call to envir takes place.
mode	the type of interest for the object.
inherits	should the enclosing frames of the environment be inspected.

See Also

get.

Examples

##  Define a substitute function if necessary:
if(!exists("some.fun", mode="function"))
 some.fun <- function(x) { cat("some.fun(x)\n"); x }

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