tree  R Documentation 
A tree is grown by binary recursive partitioning using the response in the specified formula and choosing splits from the terms of the righthandside.
tree(formula, data, weights, subset, na.action = na.pass, control = tree.control(nobs, ...), method = "recursive.partition", split = c("deviance", "gini"), model = FALSE, x = FALSE, y = TRUE, wts = TRUE, ...)
formula 
A formula expression. The lefthandside (response)
should be either a numerical vector when a regression tree will be
fitted or a factor, when a classification tree is produced. The
righthandside should be a series of numeric or factor
variables separated by 
data 
A data frame in which to preferentially interpret

weights 
Vector of nonnegative observational weights; fractional weights are allowed. 
subset 
An expression specifying the subset of cases to be used. 
na.action 
A function to filter missing data from the model
frame. The default is 
control 
A list as returned by 
method 
character string giving the method to use. The only other
useful value is 
split 
Splitting criterion to use. 
model 
If this argument is itself a model frame, then the

x 
logical. If true, the matrix of variables for each case is returned. 
y 
logical. If true, the response variable is returned. 
wts 
logical. If true, the weights are returned. 
... 
Additional arguments that are passed to

A tree is grown by binary recursive partitioning using the response in the specified formula and choosing splits from the terms of the righthandside. Numeric variables are divided into X < a and X > a; the levels of an unordered factor are divided into two nonempty groups. The split which maximizes the reduction in impurity is chosen, the data set split and the process repeated. Splitting continues until the terminal nodes are too small or too few to be split.
Tree growth is limited to a depth of 31 by the use of integers to label nodes.
Factor predictor variables can have up to 32 levels. This limit is imposed for ease of labelling, but since their use in a classification tree with three or more levels in a response involves a search over 2^(k1)  1 groupings for k levels, the practical limit is much less.
The value is an object of class "tree"
which has components
frame 
A data frame with a row for each node, and

where 
An integer vector giving the row number of the frame detailing the node to which each case is assigned. 
terms 
The terms of the formula. 
call 
The matched call to 
model 
If 
x 
If 
y 
If 
wts 
If 
and attributes xlevels
and, for classification trees,
ylevels
.
A tree with no splits is of class "singlenode"
which inherits
from class "tree"
.
B. D. Ripley
Breiman L., Friedman J. H., Olshen R. A., and Stone, C. J. (1984) Classification and Regression Trees. Wadsworth.
Ripley, B. D. (1996) Pattern Recognition and Neural Networks. Cambridge University Press, Cambridge. Chapter 7.
tree.control
, prune.tree
,
predict.tree
, snip.tree
data(cpus, package="MASS") cpus.ltr < tree(log10(perf) ~ syct+mmin+mmax+cach+chmin+chmax, cpus) cpus.ltr summary(cpus.ltr) plot(cpus.ltr); text(cpus.ltr) ir.tr < tree(Species ~., iris) ir.tr summary(ir.tr)
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