Change the class of an object to indicate that it should be treated ‘as is’.
A copy of the object with class
"AsIs" prepended to the class(es).
I has two main uses.
data.frame. Protecting an object by
enclosing it in
I() in a call to
data.frame inhibits the
conversion of character vectors to factors and the dropping of
names, and ensures that matrices are inserted as single columns.
I can also be used to protect objects which are to be
added to a data frame, or converted to a data frame via
It achieves this by prepending the class
"AsIs" to the object's
"AsIs" has a few of its own methods, including
formula. There it is used to
inhibit the interpretation of operators such as
"^" as formula operators, so they
are used as arithmetical operators. This is interpreted as a symbol
Chambers, J. M. (1992) Linear models. Chapter 4 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.