terms.object {base}

R Documentation

Description of Terms Objects

Description

An object of class terms holds information about a model. Usually the model was specified in terms of a formula and that formula was used to determine the terms object.

The object itself is simply the formula supplied to the call of terms.formula. The object has a number of attributes and they are used to construct the model frame.

Value

An object with the following attributes:

factors	A matrix of variables by terms showing which variables appear in which terms.
term.labels	A character vector containing the labels for each of the terms in the model.
variables	A list of the variables in the model
intercept	Either 0, indicating no intercept is to be fit, or 1 indicating that an intercept is to be fit.
order	A vector of the same length as term.labels indicating the order of interaction for each term
response	The index of the variable (in variables) of the response (the left hand side of the formula).
offset	If the model contains offset terms there is an offset attribute indicating which terms are offsets
specials	If the specials argument was given to terms.formula there is a specials attribute, a list of vectors indicating the terms that contain these special functions.

The object has class c("terms", "formula").

Note

These objects are different from those found in S. In particular there is no formula attribute, instead the object is itself a formula. Thus, the mode of a terms object is different as well.

An example of the specials argument can be seen in the aov function.

See Also

terms, terms.default, formula.

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