Traverse: Traverse a tree or a sub-tree

Description Usage Arguments Details Value See Also

View source: R/node_methods_traversal.R

Description

Traverse takes the root of a tree or a sub-tree, and "walks" the tree in a specific order. It returns a list of Node objects, filtered and pruned by filterFun and pruneFun.

Usage

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Traverse(
  node,
  traversal = c("pre-order", "post-order", "in-order", "level", "ancestor"),
  pruneFun = NULL,
  filterFun = NULL
)

Arguments

node

the root of a tree or a sub-tree that should be traversed

traversal

any of 'pre-order' (the default), 'post-order', 'in-order', 'level', 'ancestor', or a custom function (see details)

pruneFun

allows providing a prune criteria, i.e. a function taking a Node as an input, and returning TRUE or FALSE. If the pruneFun returns FALSE for a Node, then the Node and its entire sub-tree will not be considered.

filterFun

allows providing a a filter, i.e. a function taking a Node as an input, and returning TRUE or FALSE. Note that if filter returns FALSE, then the node will be excluded from the result (but not the entire subtree).

Details

The traversal order is as follows. (Note that these descriptions are not precise and complete. They are meant for quick reference only. See the data.tree vignette for a more detailed description).

pre-order

Go to first child, then to its first child, etc.

post-order

Go to the first branch's leaf, then to its siblings, and work your way back to the root

in-order

Go to the first branch's leaf, then to its parent, and only then to the leaf's sibling

level

Collect root, then level 2, then level 3, etc.

ancestor

Take a node, then the node's parent, then that node's parent in turn, etc. This ignores the pruneFun

function

You can also provide a function, whose sole parameter is a Node object. The function is expected to return the node's next node, a list of the node's next nodes, or NULL.

Value

a list of Nodes

See Also

Node

Get

Set

Do


data.tree documentation built on Aug. 3, 2020, 5:12 p.m.