predict.rpart {rpart}  R Documentation 
Returns a vector of predicted responses from a fitted rpart
object.
## S3 method for class 'rpart': predict(object, newdata = list(), type = c("vector", "prob", "class", "matrix"), ...)
object 
fitted model object of class rpart . This is assumed to be
the result of some function that produces an object with the same named
components as that returned by the rpart function.

newdata 
data frame containing the values at which predictions are required.
The predictors referred to in the right side of
formula(object) must be present by name in newdata .
If missing, the fitted values are returned.

type 
character string denoting the type of predicted value returned. If
the rpart object is a classification tree, then the default is to
return prob predictions, a matrix whose columns are the
probability of the first, second, etc. class. (This agrees with the
default behavior of tree ). Otherwise, a vector
result is returned.

... 
further arguments passed to or from other methods. 
This function is a method for the generic function predict for class
rpart
. It can be invoked by calling predict
for an object
of the appropriate class, or directly by calling predict.rpart
regardless of the class of the object.
A new object is obtained by
dropping newdata
down the object. For factor predictors, if an
observation contains a level not used to grow the tree, it is left at
the deepest possible node and frame$yval
at the node is the
prediction.
If type="vector"
:
vector of predicted responses.
For regression trees this is the mean response at the node, for Poisson
trees it is the estimated response rate, and for classification trees
it is the predicted class.
If type="prob"
:
(for a classification tree) a matrix of class probabilities.
If type="matrix"
:
a matrix of the full responses (frame$yval2
if this exists,
otherwise frame$yval
).
For regression trees, this is the mean response, for Poisson trees it
is the response rate and the number of events at that node in the fitted
tree, and for classification trees it is the concatonation of the
predicted class, the class counts at that node in the fitted tree, and
the class probabilities.
If type="class"
:
(for a classification tree) a factor of classifications based on the
responses.
z.auto < rpart(Mileage ~ Weight, car.test.frame) predict(z.auto) fit < rpart(Kyphosis ~ Age + Number + Start, data=kyphosis) predict(fit, type="prob") # class probabilities (default) predict(fit, type="vector") # level numbers predict(fit, type="class") # factor predict(fit, type="matrix") # level number, class frequencies, probabilities sub < c(sample(1:50, 25), sample(51:100, 25), sample(101:150, 25)) fit < rpart(Species ~ ., data=iris, subset=sub) fit table(predict(fit, iris[sub,], type="class"), iris[sub, "Species"])