Identity Function

DESCRIPTION:

Returns the value of the given expression, with class AsIs.

USAGE:

I(expr) 

REQUIRED ARGUMENTS:

expr
any S-PLUS expression.

VALUE:

the value of the expression, with added class "AsIs"

DETAILS:

This function is generally used in formulas or as an argument to data.frame, with the purpose of suppressing conventional conversion of whatever expr evaluates to. For example, a matrix or list that would normally be broken up in to separate variables by data.frame will be kept intact if it is supplied as an argument to I.

SEE ALSO:

.

EXAMPLES:

lm(y ~ I(x/z)) # without I(), "/" means nesting