Graphology DOT Utilities

Graphviz DOT parser & writer for graphology.

For more information about the Graphviz DOT file format, see the DOT Language documentation.

Installation

npm install graphology-dot

Usage

• Parser
• Writer

Parser

The parser takes a graphology constructor and a DOT string, returning a graphology graph instance.

var Graph = require('graphology');

// Node
var dot = require('graphology-dot');
// Browser
var dot = require('graphology-dot/browser');

// Reading a string
var graph = dot.parse(Graph, string);

// Passing options
var graph = dot.parse(Graph, string, {addMissingNodes: true});

Arguments

• constructor GraphClass: graphology constructor to use.
• source string: DOT string to parse.
• options ?object: parsing options:
  • addMissingNodes ?boolean [false]: whether to add missing nodes referenced in edge statements. In DOT, nodes are commonly defined implicitly through edges, so missing nodes are always added automatically regardless of this option.

Supported DOT Features

• graph / digraph / strict graph / strict digraph declarations
• Node statements with attributes: nodeID [key=value, ...]
• Edge statements: n1 -- n2 (undirected) / n1 -> n2 (directed)
• Edge chains: a -> b -> c -> d
• Attribute statements for defaults: graph [...], node [...], edge [...]
• Subgraphs (named and anonymous): subgraph S { ... } / { ... }
• Comments: // line, /* block */, # line
• Quoted node IDs and attribute values: "node name" [label="A Label"]
• Numeric node IDs: 1, 42
• Port/compass syntax: node:port, node:port:compass
• HTML-like labels: <b>bold</b>

Attribute Type Inference

Attribute values are automatically cast to the appropriate JavaScript type:

• true / false → boolean
• 42, 3.14, -1 → number
• "hello" → string
• bareword → string
• Bare key without value (e.g. [active]) → true

Writer

The writer takes a graphology instance and outputs a DOT string.

// Node
var dot = require('graphology-dot');
// Browser
var dot = require('graphology-dot/browser');

// Writing the graph
var dotString = dot.write(graph);

// Using custom formatting for nodes & edges
var dotString = dot.write(graph, {
  formatNode: function (key, attributes) {
    return {
      label: attributes.label,
      color: attributes.color,
      size: attributes.size
    };
  },
  formatEdge: function (key, attributes) {
    return {
      weight: attributes.weight,
      active: attributes.active
    };
  }
});

Arguments

• graph Graph: graphology instance to write.
• options ?object: Options:
  • formatNode ?function: function receiving (key, attributes) and returning the node's data to write. Defaults to writing all attributes.
  • formatEdge ?function: function receiving (key, attributes) and returning the edge's data to write. Defaults to writing all attributes.

Writer Behavior

• Undirected/mixed graphs use the graph keyword; directed graphs use digraph.
• The graph's id attribute becomes the graph name: graph G { ... }.
• Other graph-level attributes are written as graph [key=value, ...].
• Attribute values are formatted according to their JavaScript type:
  • Booleans → true / false
  • Numbers → unquoted literal (42, 3.14)
  • Simple string identifiers → unquoted (red)
  • Strings with special characters → quoted ("hello world")