This help topic is for R version 2.9.0. For the current version of R, try https://stat.ethz.ch/R-manual/R-patched/library/base/html/is.object.html
is.object {base}R Documentation

Is an Object “internally classed”?

Description

A function rather for internal use. It returns TRUE if the object x has the R internal OBJECT bit set, and FALSE otherwise. The OBJECT bit is set when a "class" attribute is added and removed when that attribute is removed, so this is a very efficient way to check if an object has a class attribute. (S4 objects always should.)

Usage

is.object(x)

Arguments

x

object to be tested.

See Also

class, and methods.

isS4.

Examples

is.object(1) # FALSE
is.object(as.factor(1:3)) # TRUE

[Package base version 2.9.0 ]