Is a Variable Defined?

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Is a Variable Defined?

Syntax

exists(x, envir=sys.frame(sys.parent()), mode="any",
        inherits=FALSE)

Arguments

`x`	a variable name (given as a quoted string).
`envir`	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.

Description

exists 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 searched for. exists returns TRUE if the variable is encountered and FALSE if not.