bootstrap
is a fairly flexible function, and can be called with
or without arguments newdata
and newenv
.
If called with only object
specified, then bootstrap estimates
for the training set data are returned. In this case, the returned
object will not include component predictions
.
If called with both object
and newdata
, then in addition
to the above, bootstrap estimates for the new samples are also
calculated and returned. In this case, component predictions
will contain the apparent and bootstrap derived predictions and
sample-specific errors for the new samples.
If called with object
, newdata
and newenv
, then
the full bootstrap
object is returned (as described in the
Value section below). With environmental data now available for the
new samples, residuals, RMSE(P) and \(R^2\) and bias statistics can
be calculated.
The individual components of predictions
are the same as those
described in the components relating to the training set data. For
example, returned.object$predictions$bootstrap
contains the
components as returned.object$bootstrap
.
It is not usual for environmental data to be available for the new
samples for which predictions are required. In normal
palaeolimnological studies, it is more likely that newenv
will
not be available as we are dealing with sediment core samples from the
past for which environmental data are not available. However, if
sufficient training set samples are available to justify producing a
training and a test set, then newenv
will be available, and
bootstrap
can accomodate this extra information and calculate
apparent and bootstrap estimates for the test set, allowing an
independent assessment of the RMSEP of the model to be performed.
Typical usage of residuals
is
resid(object, which = c("model", "bootstrap"), \dots)