R: Traverse a tree or a sub-tree

Traverse {data.tree}

R Documentation

Traverse a tree or a sub-tree

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

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