# Graph Algorithm

Graph algorithms provide one of the most effective methods for analyzing relational data. They describe how to process graphs to discover some qualitative or quantitative measures. Graph algorithms are based on graph theory and use the relationship between them to structure and change complex systems. We can use these algorithms to discover hidden information, verify business assumptions, and change behavior to make predictions.

If you are interested in data structures and algorithms, you can learn from javascript-algorithms.

G6 has added graph algorithms since V3.5. In future versions, we will continue to enrich the built-in algorithms.

New Feature in「v4.2.2」

GADDI Graph Pattern Macthing supports structure and semantic matching. Give a graph data and a pattern data with specific semantic clustering infomation, it returns the same and similar sub structures on the origin graph data. DEMO Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueThe origin graph data
patternGraphDatatrueThe pattern graph data to be matched
knumberfalseThe parameter for GADDI, it will be calculated automatically when it is `undefined`
lengthnumberfalseThe parameter for GADDI, it will be calculated automatically when it is `undefined`
nodeLabelPropnumberfalseThe name of the cluster property in the nodes data
edgeLabelPropnumberfalseThe name of the cluster property in the edges data

Usage

``````import G6, { Algorithm } from '@antv/g6'
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500
})

const graphData = {
nodes: [
{ id: 'A', cluster: 'nc1' },
{ id: 'B', cluster: 'nc1' },
{ id: 'C', cluster: 'nc2' },
{ id: 'D', cluster: 'nc1' },
{ id: 'E', cluster: 'nc3' },
],
edges: [
{ source: 'A', target: 'B', cluster: 'ec1' },
{ source: 'B', target: 'C', cluster: 'ec2' },
{ source: 'A', target: 'D', cluster: 'ec1' },
{ source: 'A', target: 'E', cluster: 'ec2' },
]
}

graph.data(data)
graph.render()

const { GADDI } = Algorithm;
const patternData = {
nodes: [
{ id: 'pn1', cluster: 'nc1' },
{ id: 'pn2', cluster: 'nc1' },
{ id: 'pn3', cluster: 'nc3' },
],
edges: [
{ source: 'pn1', target: 'pn2', cluster: 'ec1' },
{ source: 'pn1', target: 'pn3', cluster: 'ec2' },
]
}
const resultMatches = GADDI(graphData, patternData, true, undefined, undefined, 'cluster', 'cluster');

console.log(resultMatches);
// output:
// [{
//   nodes: [
//     { id: 'A', cluster: 'nc1' },
//     { id: 'B', cluster: 'nc1' },
//     { id: 'E', cluster: 'nc3' },],
//   edges: [
//     { source: 'A', target: 'B', cluster: 'ec1' },
//     { source: 'A', target: 'E', cluster: 'ec2' }
//   ]
// }]``````

### depthFirstSearch

Depth first search (DFS) is an algorithm for traversing or searching tree or graph data structures. One starts at the root (selecting some arbitrary node as the root in the case of a graph) and explores as far as possible along each branch before backtracking. Image Source

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. Note that it should be assigned with graph instance to this parameter instead before v4.1.0
startNodeIdstringtrueThe ID of the node to be started
callbacksIAlgorithmCallbacksfalseThe callback function

Usage

``````import G6, { Algorithm } from '@antv/g6';
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});

const data = {
nodes: [
{ id: 'A' },
{ id: 'B' },
{ id: 'C' },
{ id: 'D' },
{ id: 'E' },
{ id: 'F' },
{ id: 'G' },
],
edges: [
{ source: 'A', target: 'B' },
{ source: 'B', target: 'C' },
{ source: 'A', target: 'C' },
{ source: 'D', arget: 'A' },
{ source: 'D', target: 'E' },
{ source: 'E', target: 'F' },
],
};

graph.data(data);
graph.render();

const { depthFirstSearch } = Algorithm;
depthFirstSearch(data, 'A', {
enter: ({ current, previous }) => {
// The callback function for the traversal's begining
},
leave: ({ current, previous }) => {
// The callback function for the traversal's ending
},
});``````

Breadth-first search (BFS) is an algorithm for traversing or searching tree or graph data structures. It starts at the tree root (or some arbitrary node of a graph, sometimes referred to as a 'search key') and explores the neighbor nodes first, before moving to the next level neighbors. Image Source

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. Note that it should be assigned with graph instance to this parameter instead before v4.1.0
startNodeIdstringtrueThe ID of the starting node
originalCallbacksIAlgorithmCallbacksfalseThe callback function

Usage

``````import G6, { Algorithm } from '@antv/g6';
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});

const data = {
nodes: [
{ id: 'A' },
{ id: 'B' },
{ id: 'C' },
{ id: 'D' },
{ id: 'E' },
{ id: 'F' },
{ id: 'G' },
],
edges: [
{ source: 'A', target: 'B' },
{ source: 'B', target: 'C' },
{ source: 'A', target: 'C' },
{ source: 'D', arget: 'A' },
{ source: 'D', target: 'E' },
{ source: 'E', target: 'F' },
],
};

graph.data(data);
graph.render();

const { breadthFirstSearch } = Algorithm;
enter: ({ current, previous }) => {
// The callback function for the traversal's begining
},
leave: ({ current, previous }) => {
// The callback function for the traversal's ending
},
});``````

### labelPropagation

Supported after G6 4.0 Label Propagation compute the clusters for graph data automatically. Compare to LOUVAIN, Label Propagation has lower time complexity.

Parameters

NameTypeRequiredDescription
dataGraphDatatrueGraph data
directedBooleanfalseWhether it is a directed graph, false by default
weightPropertyNameStringfalseThe property name of the edge weight, `'weight' by default. If there is no weight in each edge, every edge has unit weight
maxIterationNumberfalseMax iteration number, 10000 by default

Return

Returns the clustered data with `clusters` and `clusterEdges` arrays. And each node data in the input `data` will be assigned with corresponding `clusterId`. The type of the return value is:

``````interface ClusterData {
clusters: {
// Clusters array
id: string; // the ID of a cluster
nodes: NodeConfig[]; // the nodes in the cluster
}[];
clusterEdges: {
// The edges between clusters
source: string; // source cluster ID
target: string; // target cluster ID
count: number; // the real edges number of this cluster edge
}[];
}``````

Example of the return value:

``````{
clusters: [
{id: 'cluster1', nodes: [ {id: 'node1', clusterId: 'cluster1'}, {id: 'node2', clusterId: 'cluster1'} ]},
{id: 'cluster2', nodes: [ {id: 'node3', clusterId: 'cluster2'} ]},
],
clusterEdges: [
{source: 'cluster1', target: 'cluster2', count: 10},
{source: 'cluster1', target: 'cluster1', count: 3},
]
}``````

Usage

``````import G6, { Algorithm } from '@antv/g6';
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});

const data = {
nodes: [
{ id: 'A' },
{ id: 'B' },
{ id: 'C' },
{ id: 'D' },
{ id: 'E' },
{ id: 'F' },
{ id: 'G' },
],
edges: [
{ source: 'A', target: 'B' },
{ source: 'B', target: 'C' },
{ source: 'A', target: 'C' },
{ source: 'D', arget: 'A' },
{ source: 'D', target: 'E' },
{ source: 'E', target: 'F' },
],
};

graph.data(data);
graph.render();

const { labelPropagation } = Algorithm;

// result includes clusters array and clusterEdges array. Each node in the data will be assigned with corresponding clusterId
let result = labelPropagation(data);``````

### louvain

Supported after G6 4.0 LOUVAIN auto clustering algorithm cluster the nodes according to the edge density between nodes. Compare to Label Propagation, LOUVAIN is more accurate.

References: https://en.wikipedia.org/wiki/Louvain_method

Parameters

NameTypeRequiredDescription
dataGraphDatatrueGraph data
directedBooleanfalseWhether it is a directed graph, false by default
weightPropertyNameStringfalseThe property name of the edge weight, `'weight' by default. If there is no weight in each edge, every edge has unit weight
thresholdNumberfalseThe convergence threshold, 0.0001 by default

Return

Returns the clustered data with `clusters` and `clusterEdges` arrays. And each node data in the input `data` will be assigned with corresponding `clusterId`. The type of the return value is:

``````interface ClusterData {
clusters: {
// Clusters array
id: string; // the ID of a cluster
nodes: NodeConfig[]; // the nodes in the cluster
sumTot?: number; // The number of edges in the cluster
}[];
clusterEdges: {
// The edges between clusters
source: string; // source cluster ID
target: string; // target cluster ID
count: number; // the real edges number of this cluster edge
}[];
}``````

Example of the return value:

``````{
clusters: [
{id: 'cluster1', sumTot: 8, nodes: [ {id: 'node1', clusterId: 'cluster1'}, {id: 'node2', clusterId: 'cluster1'} ]},
{id: 'cluster2', sumTot: 15, nodes: [ {id: 'node3', clusterId: 'cluster2'} ]},
],
clusterEdges: [
{source: 'cluster1', target: 'cluster2', count: 10},
{source: 'cluster1', target: 'cluster1', count: 3},
]
}``````

Usage

``````import G6, { Algorithm } from '@antv/g6';
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});

const data = {
nodes: [
{ id: 'A' },
{ id: 'B' },
{ id: 'C' },
{ id: 'D' },
{ id: 'E' },
{ id: 'F' },
{ id: 'G' },
],
edges: [
{ source: 'A', target: 'B' },
{ source: 'B', target: 'C' },
{ source: 'A', target: 'C' },
{ source: 'D', arget: 'A' },
{ source: 'D', target: 'E' },
{ source: 'E', target: 'F' },
],
};

graph.data(data);
graph.render();

const { louvain } = Algorithm;

// result includes clusters array and clusterEdges array. Each node in the data will be assigned with corresponding clusterId
let result = louvain(data);``````

### detectDirectedCycle

In a given directed graph, check whether a ring is included. If at least one ring is included in the given graph, the first ring included is returned. Returns `null` if there is no cycle in the graph.

References:

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. Note that it should be assigned with graph instance to this parameter instead before v4.1.0

Return

Returns the detected cycle. Returns `null` if there is no cycle.

Usage

``````import G6, { Algorithm } from '@antv/g6';
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});

const data = {
nodes: [
{ id: 'A' },
{ id: 'B' },
{ id: 'C' },
{ id: 'D' },
{ id: 'E' },
{ id: 'F' },
{ id: 'G' },
],
edges: [
{ source: 'A', target: 'B' },
{ source: 'B', target: 'C' },
{ source: 'A', target: 'C' },
{ source: 'D', arget: 'A' },
{ source: 'D', target: 'E' },
{ source: 'E', target: 'F' },
],
};

graph.data(data);
graph.render();

const { detectDirectedCycle } = Algorithm;

// There is no cycle in the graph, the result is null
let result = detectDirectedCycle(data);

// There will be a cycle after adding edge F->D
data.edges.push({
source: 'F',
target: 'D',
});

graph.changeData(data);

// Returns:
/**
* {
D: Node,
F: Node,
E: Node,
}
*/
result = detectDirectedCycle(data);``````

### detectAllCycles(graphData, directed, nodeIds, include)

Find all simple cycles (elementary circuits) of a directed graph, and for undirected graph, find a list of cycles which form a basis for cycles of graph.

References:

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. Note that it should be assigned with graph instance to this parameter instead before v4.1.0
directedbooleanfalseWhether the graph is directed, use the value of `graph.get('directed')` by default. ｜
nodeIdsstring[]falseThe nodes that should be included in or excluded from the cycles. If not configured, return all of the cycles.｜
includebooleanfalseIf it is `true`, the returned cycles shuld include one of the nodes in `nodeIds`, otherwise the cycles should not have any nodes in `nodeIds`. `true` by default.｜

Return

• Type of return value: [{[key: string]: Node}]
• Return a list of cyles. Each cycle is an object, whose key is a node ID and whose value is its next node in the cycle.

Usage

``````const { detectAllCycles } = Algorithm;

const allCycles = detectAllCycles(data, true);

// Find all cycles that includes node B
const allCycleIncludeB = detectAllCycles(data, true, ['B']);

// Find all cycles that does not includes node B
const allCycleExcludeB = detectAllCycles(data, false, ['B'], false);``````

### findShortestPath(graphData, start, end, directed, weightPropertyName)

Compute the shortest path between two nodes in the graph.

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. Note that it should be assigned with graph instance to this parameter instead before v4.1.0
startINode / stringtrueG6 Node Instance or node ID, indicating the start of the path ｜
endINode / stringtrueG6 Node Instance or node ID, indicating the end of the path ｜
directedbooleanfalseWhether the graph is directed, use the value of `graph.get('directed')` by default. ｜
weightPropertyNamestringfalseConfigure the edge property as the edge weight. If not configured, every edge has weight 1.｜

Return

• Type of return value: Object，
`````` {
length: number, // the length of the path
path: string[], // the node IDs that form the path
allPath: string[][] // all the shortest path from the start to the end
}``````

Usage

``````const data = {
nodes: [
{
id: 'A',
label: 'A',
},
{
id: 'B',
label: 'B',
},
{
id: 'C',
label: 'C',
},
{
id: 'D',
label: 'D',
},
{
id: 'E',
label: 'E',
},
{
id: 'F',
label: 'F',
},
{
id: 'G',
label: 'G',
},
{
id: 'H',
label: 'H',
},
],
edges: [
{
source: 'A',
target: 'B',
},
{
source: 'B',
target: 'C',
},
{
source: 'C',
target: 'G',
},
{
source: 'A',
target: 'D',
},
{
source: 'A',
target: 'E',
},
{
source: 'E',
target: 'F',
},
{
source: 'F',
target: 'D',
},
{
source: 'D',
target: 'E',
},
],
};

const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});
graph.data(data);
graph.render();

const { findShortestPath } = Algorithm;
// Find the shortest path between node A and node C in this undirected graph
const { length, path, allPath } = findShortestPath(data, 'A', 'C');
console.log(length, path);
// Expected output: 2, ['A', 'B', 'C']``````

### findAllPath(graphData, start, end, directed)

Find all paths between two nodes in the graph.

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. . Note that it should be assigned with graph instance to this parameter instead before v4.1.0
startINode / stringtrueG6 Node Instance or node ID, indicating the start of the path ｜
endINode / stringtrueG6 Node Instance or node ID, indicating the end of the path ｜
directedbooleanfalseWhether the graph is directed, use the value of `graph.get('directed')` by default. ｜

Return

• Type of return value: string[][]
• Return a list of paths, in which each path is an array of node IDs.

Usage

``````const data = {
nodes: [
{
id: 'A',
label: 'A',
},
{
id: 'B',
label: 'B',
},
{
id: 'C',
label: 'C',
},
{
id: 'D',
label: 'D',
},
{
id: 'E',
label: 'E',
},
{
id: 'F',
label: 'F',
},
{
id: 'G',
label: 'G',
},
{
id: 'H',
label: 'H',
},
],
edges: [
{
source: 'A',
target: 'B',
},
{
source: 'B',
target: 'C',
},
{
source: 'C',
target: 'G',
},
{
source: 'A',
target: 'D',
},
{
source: 'A',
target: 'E',
},
{
source: 'E',
target: 'F',
},
{
source: 'F',
target: 'D',
},
{
source: 'D',
target: 'E',
},
],
};

const graph = new G6.Graph({
container: 'container',
width: 500,
height: 500,
});
graph.data(data);
graph.render();

const { findAllPath } = Algorithm;
const allPath = findAllPath(data, 'A', 'E');
console.log(allPath);
// Expected output: [['A', 'D', 'F', 'E'], ['A', 'D', 'E'], ['A', 'E']]``````

### getConnectedComponents

Find the connect component of the graph. In the case of a directed graph, the strongly connected components are returned.

Translated with www.DeepL.com/Translator (free version)

Reference:

• Detect the strongly connected components in a directed graph: Tarjan's Algorithm

Parameters

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. . Note that it should be assigned with graph instance to this parameter instead before v4.1.0
directedbooleanfalseWhether the graph is directed, use the value of `graph.get('directed')` by default. ｜

Return

• Type of return value: INode[][]
• Return a list of connected components or strongly-connect components. Each component is a list of node instances.

Usage

``````const data = {
nodes: [
{
id: 'A',
},
{
id: 'B',
},
{
id: 'C',
},
{
id: 'D',
},
{
id: 'E',
},
{
id: 'F',
},
{
id: 'G',
},
{
id: 'H',
},
],
edges: [
{
source: 'A',
target: 'B',
},
{
source: 'B',
target: 'C',
},
{
source: 'A',
target: 'C',
},
{
source: 'D',
target: 'A',
},
{
source: 'D',
target: 'E',
},
{
source: 'E',
target: 'F',
},
{
source: 'F',
target: 'D',
},
{
source: 'G',
target: 'H',
},
{
source: 'H',
target: 'G',
},
],
};
const graph = new G6.Graph({
container: 'container',
width: 500,
height: 400,
});
graph.data(data);
graph.render();

// Connected components
const components = getConnectedComponents(data, false);
components.forEach((component) => {
console.log(component.map((node) => node.get('id')));
});
// Expected output: ['A', 'B', 'C', 'D', 'E', 'F'], ['G', 'H']

// Strongly-connected components
const components2 = getConnectedComponents(data, true);
components2.forEach((component) => {
console.log(component.map((node) => node.get('id')));
});
// Expected output: ['A'], ['B'], ['C'], ['D', 'E', 'F'], ['G', 'H']``````

### pageRank

The PageRank algorithm assumes that the importance of the current node is determined by the importance of other nodes pointing to it, and that the more inbound links a node receives from other nodes, the more important it is. PageRank is determined by counting the number and quality of links to a node.

Reference:

NameTypeRequiredDescription
graphDataGraphDatatrueGraph data in G6 data format. Note that it should be assigned with graph instance to this parameter instead before v4.1.0
epsilonnumberfalseThe precision level used to identify whether the calculation is converged. ｜
linkProbnumberfalseThe the probability that the outgoing links will be visited next, 0.85 by default.｜

Return

• Type of return value: Object, {[key: string]: number}
• The PageRank value for each node.