gbm: pretty.gbm.tree – R documentation

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pretty.gbm.tree

Print gbm tree components

Description

gbm stores the collection of trees used to construct the model in a compact matrix structure. This function extracts the information from a single tree and displays it in a slightly more readable form. This function is mostly for debugging purposes and to satisfy some users' curiosity.

Usage

## S3 method for class 'gbm.tree'
pretty(object, i.tree = 1)

Arguments

`object`	a `gbm.object` initially fit using `gbm`
`i.tree`	the index of the tree component to extract from `object` and display

Value

pretty.gbm.tree returns a data frame. Each row corresponds to a node in the tree. Columns indicate

`SplitVar`	index of which variable is used to split. -1 indicates a terminal node.
`SplitCodePred`	if the split variable is continuous then this component is the split point. If the split variable is categorical then this component contains the index of `object$c.split` that describes the categorical split. If the node is a terminal node then this is the prediction.
`LeftNode`	the index of the row corresponding to the left node.
`RightNode`	the index of the row corresponding to the right node.
`ErrorReduction`	the reduction in the loss function as a result of splitting this node.
`Weight`	the total weight of observations in the node. If weights are all equal to 1 then this is the number of observations in the node.

Author(s)

Greg Ridgeway gregridgeway@gmail.com