Tree layout

Arranges a rooted hierarchy: leaves spread left-to-right in merge-side order and internal nodes sit at the mean leaf position of their children. Self-contained (no external dependency). Edges must point from parent to child; multiple roots (forests) are supported.

Usage

layout_tree(
  plot,
  direction = c("down", "up", "left", "right"),
  leaf_spacing = "count",
  edge = "straight"
)

Arguments

plot

A plotit object holding graph data (created via as_graph() + plotit()), or a bare plotit_graph.

direction

Direction the tree grows: "down" (root on top), "up", "right", or "left".

leaf_spacing

Leaf placement: "count" packs leaves one unit apart in merge-side order (d3 tidy-tree); "equal" normalises leaves onto [0, 1] so leaf slots align with split-facet panels.

edge

Edge shape: "straight" (direct parent-child segments) or "elbow" (right-angle bend via a midpoint row pair; each edge becomes two rows in the edges table so mark_rule() renders the polyline).

Value

A modified plotit object (pipeline form), or a new plotit_graph when called on raw graph data.

Examples

h <- data.frame(
  id     = c("root", "A", "B", "a1", "a2"),
  parent = c(NA, "root", "root", "A", "A")
)
as_graph(h) |>
  plotit() |>
  layout_tree(direction = "down") |>
  mark_rule(data = ~edges) |>
  mark_point(data = ~nodes)


as_graph(h) |>
  plotit() |>
  layout_tree(direction = "right", edge = "elbow") |>
  mark_rule(data = ~edges) |>
  mark_point(data = ~nodes)