model.extract | R Documentation |
Returns the response, offset, subset, weights or other
special components of a model frame passed as optional arguments to
model.frame
.
model.extract(frame, component) model.offset(x) model.response(data, type = "any") model.weights(x)
frame, x, data |
A model frame. |
component |
literal character string or name. The name of a
component to extract, such as |
type |
One of |
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.extract(m, "offset")
and model.extract(m, "response")
are equivalent to model.offset(m)
and model.response(m)
respectively. model.offset
sums any terms specified by
offset
terms in the formula or by offset
arguments
in the call producing the model frame: it does check that the offset
is numeric.
model.weights
is slightly different from
model.extract(, "weights")
in not naming the vector it returns.
The specified component of the model frame, usually a vector.
model.response()
now drops a possible "Asis"
class
(stemming from I(.)
).
model.frame
, offset
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) (mw <- model.extract(a, "weights")) stopifnot(identical(unname(mw), model.weights(a))) a <- model.frame(cbind(ncases,ncontrols) ~ agegp, something = tobgp, data = esoph) names(a) stopifnot(model.extract(a, "something") == esoph$tobgp)
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