Update an earth model
Update an earth model.
## S3 method for class 'earth'
update(object = stop("no 'object' argument"),
formula. = NULL, ponly = FALSE, ..., evaluate = TRUE)object |
The earth object |
formula. |
The |
ponly |
Force pruning only, no forward pass.
Default is |
... |
Arguments passed on to |
evaluate |
If |
If only the following arguments are used, a forward pass
is unnecessary, and update.earth will perform only the pruning pass.
This is usually much faster for large models.
object
glm
trace
nprune
pmethod
Eval.model.subsets
Print.pruning.pass
Force.xtx.prune
Use.beta.cache
Endspan.penalty
Get.leveragesThis automatic determination to do a forward pass can be overridden
with the ponly argument.
If ponly=TRUE the forward pass will be skipped and only the pruning pass will be executed.
This is useful for doing a pruning pass with new data.
(Use earth's data argument to specify the new data.)
Typically in this scenario you would also specify penalty=-1.
This is because with sufficient new data, independent of the original
training data, the RSS not the GCV should be used for evaluating model
subsets
(The GCV approximates what the RSS would be on new data — but here
we actually have new data, so why bother approximating.
This "use new data for pruning" approach is useful in situations where
you don't trust the GCV approximation for your data.)
By making penalty=-1, earth will calculate the RSS, not the GCV.
See also the description of penalty on the
earth help page.
Another (somewhat esoteric) use of ponly=TRUE is to do subset
selection with a different penalty from that used to build the
original model.
With trace=1, update.earth will tell you if earth's
forward pass was skipped.
If you used keepxy=TRUE in your original call to earth, then
update.earth will use the saved values of x, y, etc.,
unless you specify otherwise by arguments to update.earth.
It can be helpful to set trace=1 to see which x and y
is used by update.earth.
The value is the same as that returned by earth.
If object is the only parameter then no changes are made
— the returned value will be the same as the original object.
data(ozone1) (earth.mod <- earth(O3 ~ ., data = ozone1, degree = 2)) update(earth.mod, formula = O3 ~ . - temp) # requires forward pass and pruning update(earth.mod, nprune = 8) # requires only pruning update(earth.mod, penalty=1, ponly=TRUE) # pruning pass only with a new penalty
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