This class of objects is returned by the
gam
function
to represent a fitted generalized additive model.
Class
gam
inherits from class
glm
, since the parametric part a
gam.object
is fit by weighted least-squares; the object returned has
all the components of a
glm
.
Objects of this class have methods for the functions
print
,
plot
,
summary
,
anova
,
predict
,
fitted
, and
step
, among others.
The following components must be included in a legitimate
gam
object.
The residuals, fitted values, coefficients and effects should be extracted
by the generic functions of the same name, rather than
by the "
$
" operator.
The
family
function returns the entire family object used in the fitting,
and
deviance
can be used to extract the deviance of the fit.
additive.predictors
,
which multiply the columns of the model matrix.
The names of the coefficients are the names of the
single-degree-of-freedom effects (the columns of the
model matrix).
If the model is overdetermined there will
be missing values in the coefficients corresponding to inestimable
coefficients.
"smooth"
component.
additive.predictors
using the inverse link function.
gam
model,
all of these components will be missing.
Each column corresponds to the strictly nonparametric part of the term,
while the parametric part is obtained from the model matrix.
This component is present only when there are smooth terms in the model.
smooth
. For smoothing splines specified by
s(x)
,
the approximate
df
will be the trace of the implicit smoother matrix minus 2.
This component is present only when there are smooth terms in the model.
smooth
.
This component is present only when there are smooth terms in the model.
smooth
, containing the approximate pointwise variances
for the columns of
smooth
.
This component is present only when there are smooth terms in the model.
lm
object:
call
,
terms
and some
others involving the numerical fit. See
lm.object
.
Chambers, J.M., and Hastie, T.J. (1991). Statistical Models in S, pp. 210-213.