Part of a whole
Rooted tree diagram
Shows parent-child relationships from a single root.
- Diagram
- Hierarchy
- Structure
What it answers
What belongs under each parent?
- Shape
- Branches descending from one root
- What it shows
- Depth, branches and ancestry.
Example
The question
How is our product catalogue organised?
Product catalogue as a tree
Illustrative data. It belongs to no company.
When to use it
Use it when
A true acyclic hierarchy.
Avoid it when
Multiple parents forced into a strict tree without explanation.
How to read it
Follow parent-child links from root to leaves.
Note
A strict tree gives each non-root node one parent.
The data you need
- Layout
- Parent-child table
- Fields
- NodeID: text; ParentID: text/blank; Label: text; Value: number when size is encoded
- One row is
- One node in a parent-child hierarchy. What is the grain?
- Rules
- Node IDs must be unique. Parents must exist. Reject cycles. Define leaf-only versus inclusive parent values.
- Optional
- Alternative: Level1,Level2...,Value. Tree diagrams can omit Value.
- Preparation
- Validate unique node IDs, parent links, roots and absence of cycles. For size-encoded hierarchies, state whether totals are leaf-only or inclusive.
- Units
- Tree levels and branch position are structural. Size-encoded components use a named value unit; parent shares divide by the chosen parent total.
Worked example
Root has childrenA, B; A has childA1. A1 is a grandchild of Root and a child of A.
| NodeID | ParentID | Label | Value |
|---|---|---|---|
| root | All | 100 | |
| a | root | A | 60 |
| b | root | B | 40 |