model.extract {stats}R Documentation

Extract Components from a Model Frame

Description

Returns the response, offset, subset, weights or other special components of a model frame passed as optional arguments to model.frame.

Usage

model.extract(frame, component)
model.offset(x)
model.response(data, type = "any")
model.weights(x)

Arguments

frame, x, data A model frame.
component literal character string or name. The name of a component to extract, such as "weights", "subset".
type One of "any", "numeric", "double". Using the either of latter two coerces the result to have storage mode "double".

Details

model.extract is provided for compatibility with S, which does not have the more specific functions. It is also useful to extract e.g. the etastart and mustart components of a glm fit.

model.offset and model.response are equivalent to model.frame(, "offset") and model.frame(, "response") respectively.

model.weights is slightly different from model.frame(, "weights") in not naming the vector it returns.

Value

The specified component of the model frame, usually a vector.

See Also

model.frame, offset

Examples

data(esoph)
a <- model.frame(cbind(ncases,ncontrols) ~ agegp+tobgp+alcgp, data=esoph)
model.extract(a, "response")
stopifnot(model.extract(a, "response") == model.response(a))

a <- model.frame(ncases/(ncases+ncontrols) ~ agegp+tobgp+alcgp,
                 data = esoph, weights = ncases+ncontrols)
model.response(a)
model.extract(a, "weights")

a <- model.frame(cbind(ncases,ncontrols) ~ agegp,
                 something = tobgp, data = esoph)
names(a)
stopifnot(model.extract(a, "something") == esoph$tobgp)
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