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Object Classes

Syntax

class(x)
class(x) <- names
unclass(x)
inherits(x, name)
is.object(x)

Description

R possesses a simple generic function mechanism which can be used for an object-oriented style of programming. Method despatch takes place based on the class of the first argument to the generic function.

An R ``object'' is a data object which has a class attribute. A class attribute is a vector of character strings giving the names of the classes which the object ``inherits'' from. When a generic function fun is applied to an object with class attribute c("first","second"), the system searches for a function called fun.first and, if it finds it, applied it to the object. If no such function is found a function called fun.second is tried. If no class name produces a suitable function, the function fun.default is used.

The function class prints the vector of names of classes which an object inherits from. Correspondingly, class<- sets the classes which an object inherits from. unclass returns (a copy of) its argument with its class information removed.

is.object returns TRUE if its argument has a class attribute and FALSE otherwise. inherits indicates whether its first argument inherits from a class with name equal to its second argument.

See Also

UseMethod, NextMethod.