C

ConnectedComponents

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Determines the connected components of a given graph.
Inheritance Hierarchy

Remarks

A graph G is called connected if there exists an undirected path of edges between every pair of nodes.

The connected components of a graph are the maximal connected subgraphs of which the graph consists.

Other Graph Connectivity Algorithms

yFiles for HTML supports a number of other analysis algorithms that partition the graph into components, based on various criteria.

  • StronglyConnectedComponents – Determines components defined by the existence of a directed path between nodes
  • BiconnectedComponents – Determines components defined by the existence of at least two separate undirected paths between all nodes
  • Bipartition – Divides a graph into two partitions where all edges have their source and target in different partitions
  • IndependentSets – Divides a graph into partitions where no nodes are connected within a partition
  • KCoreComponents – Calculates the k-cores of an undirected input graph. The k-core of an undirected input graph consists of the subgraph components where each node has at least degree k.

Complexity

O(|V| + |E|)

Examples

Calculating connected components on a graph
// prepare the connected components algorithm
const algorithm = new ConnectedComponents()
// run the algorithm
const result = algorithm.run(graph)

// highlight the nodes of the connected components with different styles
for (const node of graph.nodes) {
  const componentId = result.nodeComponentIds.get(node)!
  graph.setStyle(node, componentStyles.get(componentId)!)
}

See Also

Developer's Guide

API

connectedComponents

Members

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Constructors

ConnectedComponents

()

Parameters

Properties

subgraphEdges

: ItemCollection<IEdge>
Gets or sets the collection of edges which define a subset of the graph for the algorithms to work on.

If nothing is set, all edges of the graph will be processed.

If only the excludes are set, all edges in the graph except those provided in the excludes are processed.

Note that edges which start or end at nodes which are not in the subgraphNodes are automatically not considered by the algorithm.

ItemCollection<T> instances may be shared among algorithm instances and will be (re-)evaluated upon (re-)execution of the algorithm.

The edges provided here must be part of the graph which is passed to the run method.
conversionfinal

Examples

Calculating connected components on a subset of the graph
// configure the connected components algorithm
const algorithm = new ConnectedComponents({
  // Ignore edges without target arrow heads
  subgraphEdges: {
    excludes: (edge: IEdge): boolean =>
      edge.style instanceof PolylineEdgeStyle &&
      edge.style.targetArrow instanceof Arrow &&
      edge.style.targetArrow.type === ArrowType.NONE,
  },
})
// run the algorithm
const result = algorithm.run(graph)

// highlight the nodes of the connected components with different styles
for (const node of graph.nodes) {
  const componentId = result.nodeComponentIds.get(node)!
  graph.setStyle(node, componentStyles.get(componentId)!)
}

subgraphNodes

: ItemCollection<INode>
Gets or sets the collection of nodes which define a subset of the graph for the algorithms to work on.

If nothing is set, all nodes of the graph will be processed.

If only the excludes are set, all nodes in the graph except those provided in the excludes are processed.

ItemCollection<T> instances may be shared among algorithm instances and will be (re-)evaluated upon (re-)execution of the algorithm.

The nodes provided here must be part of the graph which is passed to the run method.
conversionfinal

Examples

Calculating connected components on a subset of the graph
// configure the connected components algorithm
const algorithm = new ConnectedComponents({
  subgraphNodes: {
    // only consider elliptical nodes in the graph
    includes: (node: INode): boolean =>
      node.style instanceof ShapeNodeStyle &&
      node.style.shape === ShapeNodeShape.ELLIPSE,
    // but ignore the first node, regardless of its shape
    excludes: graph.nodes.first()!,
  },
})
// run the algorithm
const result = algorithm.run(graph)

// highlight the nodes of the connected components with different styles
for (const node of graph.nodes) {
  const componentId = result.nodeComponentIds.get(node)!
  graph.setStyle(node, componentStyles.get(componentId)!)
}

Methods

run

(graph: IGraph): ConnectedComponentsResult
Determines the connected components of a given graph.
The result obtained from this algorithm is a snapshot which is no longer valid once the graph has changed, e.g. by adding or removing nodes or edges.
final

Parameters

graph: IGraph
The input graph to run the algorithm on.

Return Value

ConnectedComponentsResult
A ConnectedComponentsResult containing the connected components of graph.

Throws

Exception ({ name: 'InvalidOperationError' })
If the algorithm can't create a valid result due to an invalid graph structure or wrongly configured properties.

Complexity

O(|V| + |E|)