R: Recursive Partitioning and Regression Trees Object

rpart.object {rpart} | R Documentation

## Recursive Partitioning and Regression Trees Object

### Description

These are objects representing fitted `rpart` trees.

### Value

`frame` | data frame with one row for each node in the tree. The `row.names` of `frame` contain the (unique) node numbers that follow a binary ordering indexed by node depth. Columns of `frame` include `var`, a factor giving the names of the variables used in the split at each node (leaf nodes are denoted by the level `"<leaf>"`), `n`, the number of observations reaching the node, `wt`, the sum of case weights for observations reaching the node, `dev`, the deviance of the node, `yval`, the fitted value of the response at the node, and `splits`, a two column matrix of left and right split labels for each node. Also included in the frame are `complexity`, the complexity parameter at which this split will collapse, `ncompete`, the number of competitor splits recorded, and `nsurrogate`, the number of surrogate splits recorded. Extra response information which may be present is in `yval2`, which contains the number of events at the node (poisson tree), or a matrix containing the fitted class, the class counts for each node, the class probabilities and the ‘node probability’ (classification trees).
`where` | an integer vector of the same length as the number of observations in the root node, containing the row number of `frame` corresponding to the leaf node that each observation falls into.
`call` | an image of the call that produced the object, but with the arguments all named and with the actual formula included as the formula argument. To re-evaluate the call, say `update(tree)`.
`terms` | an object of class `c("terms", "formula")` (see `terms.object`) summarizing the formula. Used by various methods, but typically not of direct relevance to users.
`splits` | a numeric matrix describing the splits: only present if there are any. The row label is the name of the split variable, and columns are `count`, the number of observations (which are not missing and are of positive weight) sent left or right by the split (for competitor splits this is the number that would have been sent left or right had this split been used, for surrogate splits it is the number missing the primary split variable which were decided using this surrogate), `ncat`, the number of categories or levels for the variable (`+/-1` for a continuous variable), `improve`, which is the improvement in deviance given by this split, or, for surrogates, the concordance of the surrogate with the primary, and `index`, the numeric split point. The last column `adj` gives the adjusted concordance for surrogate splits. For a factor, the `index` column contains the row number of the csplit matrix. For a continuous variable, the sign of `ncat` determines whether the subset `x < cutpoint` or `x > cutpoint` is sent to the left.
`csplit` | an integer matrix. (Only present only if at least one of the split variables is a factor or ordered factor.) There is a row for each such split, and the number of columns is the largest number of levels in the factors. Which row is given by the `index` column of the `splits` matrix. The columns record `1` if that level of the factor goes to the left, `3` if it goes to the right, and `2` if that level is not present at this node of the tree (or not defined for the factor).
`method` | character string: the method used to grow the tree. One of `"class"`, `"exp"`, `"poisson"`, `"anova"` or `"user"` (if splitting functions were supplied).
`cptable` | a matrix of information on the optimal prunings based on a complexity parameter.
`variable.importance` | a named numeric vector giving the importance of each variable. (Only present if there are any splits.) When printed by `summary.rpart` these are rescaled to add to 100.
`numresp` | integer number of responses; the number of levels for a factor response.
`parms, control` | a record of the arguments supplied, which defaults filled in.
`functions` | the `summary`, `print` and `text` functions for method used.
`ordered` | a named logical vector recording for each variable if it was an ordered factor.
`na.action` | (where relevant) information returned by `model.frame` on the special handling of `NA`s derived from the `na.action` argument.

There may be attributes `"xlevels"` and `"levels"` recording the levels of any factor splitting variables and of a factor response respectively.

Optional components include the model frame (`model`), the matrix of predictors (`x`) and the response variable (`y`) used to construct the `rpart` object.

### Structure

The following components must be included in a legitimate `rpart` object.

### See Also

`rpart`.

[Package rpart version 4.1-8 Index]