# Graph documentation

## Overview

Graph is a visualization to display graphs and networks consisting of nodes and edges. The visualization is easy to use and supports custom shapes, styles, colors, sizes, images, and more.

The graph visualization works smooth on any modern browser for up to a few hundred nodes and edges.

To get started with Graph, install or download the vis.js library.

## Contents

- Overview
- Example
- Loading
- Data format
  - Nodes
  - Edges
  - DOT language
- Configuration options
  - Nodes
  - Edges
  - Groups
  - Clustering
  - Navigation controls
  - Keyboard navigation
- Methods
- Events
- Data policy

## Example

Here a basic graph example. Note that unlike the Timeline, the Graph does not need the vis.css file.

More examples can be found in the examples directory.

    <!doctype html>
    <html>
    <head>
      <title>Graph | Basic usage</title>

      <script type="text/javascript" src="../../dist/vis.js"></script>
    </head>

    <body>

    <div id="mygraph"></div>

    <script type="text/javascript">
      // create an array with nodes
      var nodes = [
        {id: 1, label: 'Node 1'},
        {id: 2, label: 'Node 2'},
        {id: 3, label: 'Node 3'},
        {id: 4, label: 'Node 4'},
        {id: 5, label: 'Node 5'}
      ];

      // create an array with edges
      var edges = [
        {from: 1, to: 2},
        {from: 1, to: 3},
        {from: 2, to: 4},
        {from: 2, to: 5}
      ];

      // create a graph
      var container = document.getElementById('mygraph');
      var data= {
        nodes: nodes,
        edges: edges,
      };
      var options = {
        width: '400px',
        height: '400px'
      };
      var graph = new vis.Graph(container, data, options);
    </script>

    </body>
    </html>

## Loading

Install or download the vis.js library. in a subfolder of your project. Include the library script in the head of your html code:

    <script type="text/javascript" src="vis/dist/vis.js"></script>

The constructor of the Graph is `vis.Graph`.

    var graph = new vis.Graph(container, data, options);

The constructor accepts three parameters:

- `container` is the DOM element in which to create the graph.
- `data` is an Object containing properties `nodes` and `edges`, which both contain an array with objects. Optionally, data may contain an `options` object. The parameter `data` is optional, data can also be set using the method `setData`. Section Data Format describes the data object.
- `options` is an optional Object containing a name-value map with options. Options can also be set using the method `setOptions`. Section Configuration Options describes the available options.

## Data format

The `data` parameter of the Graph constructor is an object which can contain different types of data. The following properties are supported in the `data` object:

- A property pair `nodes` and `edges`, both containing an Array with objects. The data formats are described in the sections Nodes and Edges. Example:

      var data = {
        nodes: [...],
        edges: [...]
      };

- A property `dot`, containing a string with data in the DOT language. DOT support is described in section DOT_language. Example:

      var data = {
        dot: '...'
      };

- A property `options`, containing an object with global options. Options can be provided as third parameter in the graph constructor as well. Section Configuration Options describes the available options.

### Nodes

Nodes typically have an `id` and `label`. A node must contain at least a property `id`. Nodes can have extra properties, used to define the shape and style of the nodes.

A JavaScript Array with nodes is constructed like:

    var nodes = [
      {
        id: 1,
        label: 'Node 1'
      },
      // ... more nodes
    ];

Nodes support the following properties:

Name | Type | Required | Description
--- | --- | --- | ---
color | String | Object | no | Color for the node.
color.background | String | no | Background color for the node.
color.border | String | no | Border color for the node.
color.highlight | String | Object | no | Color of the node when selected.
color.highlight.background | String | no | Background color of the node when selected.
color.highlight.border | String | no | Border color of the node when selected.
group | Number | String | no | A group number or name. The type can be `number`, `string`, or an other type. All nodes with the same group get the same color schema.
fontColor | String | no | Font color for label in the node.
fontFace | String | no | Font face for label in the node, for example "verdana" or "arial".
fontSize | Number | no | Font size in pixels for label in the node.
id | Number | String | yes | A unique id for this node. Nodes may not have duplicate id's. Id's do not need to be consecutive. An id is normally a number, but may be any type.
image | string | no | Url of an image. Only applicable when the shape of the node is `image`.
radius | number | no | Radius for the node. Applicable for all shapes except `box`, `circle`, `ellipse` and `database`. The value of `radius` will override a value in property `value`.
shape | string | no | Define the shape for the node. Choose from `ellipse` (default), `circle`, `box`, `database`, `image`, `label`, `dot`, `star`, `triangle`, `triangleDown`, and `square`. In case of `image`, a property with name `image` must be provided, containing image urls. The shapes `dot`, `star`, `triangle`, `triangleDown`, and `square`, are scalable. The size is determined by the properties `radius` or `value`. When a property `label` is provided, this label will be displayed inside the shape in case of shapes `box`, `circle`, `ellipse`, and `database`. For all other shapes, the label will be displayed right below the shape.
label | string | no | Text label to be displayed in the node or under the image of the node. Multiple lines can be separated by a newline character `\n` .
title | string | no | Title to be displayed when the user hovers over the node. The title can contain HTML code.
value | number | no | A value for the node. The radius of the nodes will be scaled automatically from minimum to maximum value. Only applicable when the shape of the node is `dot`. If a `radius` is provided for the node too, it will override the radius calculated from the value.
x | number | no | Horizontal position in pixels. The horizontal position of the node will be fixed. The vertical position y may remain undefined.
y | number | no | Vertical position in pixels. The vertical position of the node will be fixed. The horizontal position x may remain undefined.

### Edges

Edges are connections between nodes. An edge must at least contain properties `from` and `to`, both referring to the `id` of a node. Edges can have extra properties, used to define the type and style.

A JavaScript Array with edges is constructed as:

    var edges = [
      {
        from: 1,
        to: 3
      },
      // ... more edges
    ];

Edges support the following properties:

Name | Type | Required | Description
--- | --- | --- | ---
color | string | no | A HTML color for the edge.
dash | Object | no | Object containing properties for dashed lines. Available properties: `length`, `gap`, `altLength`.
dash.altLength | number | no | Length of the alternated dash in pixels on a dashed line. Specifying `dash.altLength` allows for creating a dashed line with a dash-dot style, for example when `dash.length=10` and `dash.altLength=5`. See also the option `dahs.length`. Only applicable when the line style is `dash-line`.
dash.length | number | no | Length of a dash in pixels on a dashed line. Only applicable when the line style is `dash-line`.
dash.gap | number | no | Length of a gap in pixels on a dashed line. Only applicable when the line style is `dash-line`.
fontColor | String | no | Font color for the text label of the edge. Only applicable when property `label` is defined.
fontFace | String | no | Font face for the text label of the edge, for example "verdana" or "arial". Only applicable when property `label` is defined.
fontSize | Number | no | Font size in pixels for the text label of the edge. Only applicable when property `label` is defined.
from | Number | String | yes | The id of a node where the edge starts. The type must correspond with the type of the node id's. This is normally a number, but can be any type.
length | number | no | The length of the edge in pixels.
style | string | no | Define a line style for the edge. Choose from `line` (default), `arrow`, `arrow-center`, or `dash-line`.
label | string | no | Text label to be displayed halfway the edge.
title | string | no | Title to be displayed when the user hovers over the edge. The title can contain HTML code.
to | Number | String | yes | The id of a node where the edge ends. The type must correspond with the type of the node id's. This is normally a number, but can be any type.
value | number | no | A value for the edge. The width of the edges will be scaled automatically from minimum to maximum value. If a `width` is provided for the edge too, it will override the width calculated from the value.
width | number | no | Width of the line in pixels. The `width` will override a specified `value`, if a `value` is specified too.

### DOT language

Graph supports data in the DOT language. To provide data in the DOT language, the `data` object must contain a property `dot` with a String containing the data.

Example usage:

    // provide data in the DOT language
    var data = {
      dot: 'digraph {1 -> 1 -> 2; 2 -> 3; 2 -- 4; 2 -> 1 }'
    };

    // create a graph
    var graph = new vis.Graph(container, data);

## Configuration options

Options can be used to customize the graph. Options are defined as a JSON object. All options are optional.

    var options = {
      width:  '100%',
      height: '400px',
      edges: {
        color: 'red',
        width: 2
      }
    };

The following options are available.

Name | Type | Default | Description
--- | --- | --- | ---
clustering | Object | none | Clustering configuration. Clustering is turned off by default. See section Clustering for an overview of the available options.
edges | Object | none | Configuration options applied to all edges. See section Edges configuration for an overview of the available options.
groups | Object | none | It is possible to specify custom styles for groups. Each node assigned a group gets the specified style. See Groups configuration for an overview of the available styles and an example.
height | String | "400px" | The height of the graph in pixels or as a percentage.
keyboard | Object | none | Configuration options for shortcuts keys. Sortcut keys are turned off by default. See section Keyboard navigation for an overview of the available options.
navigation | Object | none | Configuration options for the navigation controls. See section Navigation controls for an overview of the available options.
nodes | Object | none | Configuration options applied to all nodes. See section Nodes configuration for an overview of the available options.
selectable | Boolean | true | If true, nodes in the graph can be selected by clicking them. Long press can be used to select multiple nodes.
stabilize | Boolean | true | If true, the graph is stabilized before displaying it. If false, the nodes move to a stabe position visibly in an animated way.
width | String | "400px" | The width of the graph in pixels or as a percentage.

### Nodes configuration

Nodes can be configured with different styles and shapes. To configure nodes, provide an object named `nodes` in the `options` for the Graph.

For example to give the nodes a custom color, shape, and size:

    var options = {
      // ...
      nodes: {
        color: {
          background: 'white',
          border: 'red',
          highlight: {
            background: 'pink',
            border: 'red'
          }
        },
        shape: 'star',
        radius: 24
      }
    };

The following options are available for nodes. These options must be created inside an object `nodes` in the graphs options object.

color | String | Object | Object | Default color of the nodes. When color is a string, the color is applied to both background as well as the border of the node.
color.background | String | "#97C2FC" | Default background color of the nodes
color.border | String | "#2B7CE9" | Default border color of the nodes
color.highlight | String | Object | Object | Default color of the node when the node is selected. In case of a string, the color is applied to both border and background of the node.
color.highlight.background | String | "#D2E5FF" | Default background color of the node when selected.
color.highlight.border | String | "#2B7CE9" | Default border color of the node when selected.
fontColor | String | "black" | Default font color for the text label in the nodes.
fontFace | String | "sans" | Default font face for the text label in the nodes, for example "verdana" or "arial".
fontSize | Number | 14 | Default font size in pixels for the text label in the nodes.
group | String | none | Default group for the nodes.
image | String | none | Default image url for the nodes. only applicable to shape `image`.
widthMin | Number | 16 | The minimum width for a scaled image. Only applicable to shape `image`.
widthMax | Number | 64 | The maximum width for a scaled image. Only applicable to shape `image`.
shape | String | "ellipse" | The default shape for all nodes. Choose from `ellipse` (default), `circle`, `box`, `database`, `image`, `label`, `dot`, `star`, `triangle`, `triangleDown`, and `square`. This shape can be overridden by a group shape, or by a shape of an individual node.
radius | Number | 5 | The default radius for a node. Only applicable to shapes `dot`, `star`, `triangle`, `triangleDown`, and `square`.
radiusMin | Number | 5 | The minimum radius for a scaled node. Only applicable to shapes `dot`, `star`, `triangle`, `triangleDown`, and `square`.
radiusMax | Number | 20 | The maximum radius for a scaled node. Only applicable to shapes `dot`, `star`, `triangle`, `triangleDown`, and `square`.

### Edges configuration

Edges can be configured with different length and styling. To configure edges, provide an object named `edges` in the `options` for the Graph.

For example to set the width of all edges to 2 pixels and give them a red color:

    var options = {
      // ...
      edges: {
        color: 'red',
        width: 2
      }
    };

The following options are available for edges. These options must be created inside an object `edges` in the graphs options object.

Name | Type | Default | Description
--- | --- | --- | ---
color | String | "#2B7CE9" | The default color of a edge.
dash | Object | Object | Object containing default properties for dashed lines. Available properties: `length`, `gap`, `altLength`.
dash.altLength | number | none | Default length of the alternated dash in pixels on a dashed line. Specifying `dash.altLength` allows for creating a dashed line with a dash-dot style, for example when `dash.length=10` and `dash.altLength=5`. See also the option `dahs.length`. Only applicable when the line style is `dash-line`.
dash.length | number | 10 | Default length of a dash in pixels on a dashed line. Only applicable when the line style is `dash-line`.
dash.gap | number | 5 | Default length of a gap in pixels on a dashed line. Only applicable when the line style is `dash-line`.
length | Number | 100 | The default length of a edge.
style | String | "line" | The default style of a edge. Choose from `line` (default), `arrow`, `arrow-center`, `dash-line`.
width | Number | 1 | The default width of a edge.

### Groups configuration

It is possible to specify custom styles for groups of nodes. Each node having assigned to this group gets the specified style. The options `groups` is an object containing one or multiple groups, identified by a unique string, the groupname.

A group can have the following styles:

    var options = {
      // ...

      groups: {
        mygroup: {
          shape: 'circle',
          color: {
            border: 'black',
            background: 'white',
            highlight: {
              border: 'yellow',
              background: 'orange'
            }
          }
          fontColor: 'red',
          fontSize: 18
        }
        // add more groups here
      }
    };

    var nodes = [
      {id: 1, label: 'Node 1'},                    // will get the default style
      {id: 2, label: 'Node 2', group: 'mygroup'},  // will get the style from 'mygroup'
      // ... more nodes
    ];

The following styles are available for groups:

Name | Type | Default | Description
--- | --- | --- | ---
color | String | Object | Object | Color of the node
color.border | String | "#2B7CE9" | Border color of the node
color.background | String | "#97C2FC" | Background color of the node
color.highlight | String | Object | "#D2E5FF" | Default color of the node when the node is selected. In case of a string, the color is applied to both border and background of the node.
color.highlight.background | String | "#D2E5FF" | Background color of the node when selected.
color.highlight.border | String | "#D2E5FF" | Border color of the node when selected.
image | String | none | Default image for the nodes. Only applicable in combination with shape `image`.
fontColor | String | "black" | Font color of the node.
fontFace | String | "sans" | Font name of the node, for example "verdana" or "arial".
fontSize | Number | 14 | Font size for the node in pixels.
shape | String | "ellipse" | Choose from `ellipse` (default), `circle`, `box`, `database`, `image`, `label`, `dot`, `star`, `triangle`, `triangleDown`, and `square`. In case of image, a property with name image must be provided, containing image urls.
radius | Number | 5 | Default radius for the node. Only applicable in combination with shapes `box` and `dot`.

### Clustering

The graph now supports dynamic clustering of nodes. This allows a user to view a very large dataset (> 50.000 nodes) without sacrificing performance. When loading a large dataset, the nodes are clustered initially (this may take a small while) to have a responsive visualization to work with. The clustering is both outside-in and inside-out. Outside-in means that nodes with only one connection will be contained, or clustered, in the node it is connected to. Inside-out clustering first determines which nodes are hubs. Hubs are defined as the nodes with the top 3% highest amount of connections (assuming normal distribution). These hubs then "grow", meaning they contain the nodes they are connected to within themselves. The edges that were connected to the nodes that are absorbed will be reconnected to the cluster.
A cluster is just a node that has references to the nodes and edges it contains. It has an internal counter to keep track of its size, which is then used to calculate the required forces. The contained nodes are removed from the global nodes index, greatly speeding up the system.
The clustering has the following user-configurable settings. The default values have been tested with the Graph examples and work well. The default state for clustering is off.

    // These variables must be defined in an options object named clustering.
    // If a variable is not supplied, the default value is used.
    var options = {
        clustering: {
          initialMaxNodes: 100,
          clusterThreshold:500,
          reduceToNodes:300,
          chainThreshold: 0.4,
          clusterEdgeThreshold: 20,
          sectorThreshold: 50,
          screenSizeThreshold: 0.2,
          fontSizeMultiplier:  4.0,
          forceAmplification:  0.6,
          distanceAmplification: 0.2,
          edgeGrowth: 11,
          nodeScaling: {width:  10,
                        height: 10,
                        radius: 10},
          activeAreaBoxSize: 100
        }
    }
    // OR to just load the module with default values:
    var options: {
        clustering: true
    }

Name | Type | Default | Description
--- | --- | --- | ---
initialMaxNodes | Number | 100 | If the initial amount of nodes is larger than this value, clustering starts until the total number of nodes is less than this value.
clusterThreshold | Number | 500 | While zooming in and out, clusters can open up. Once there are more than `absoluteMaxNumberOfNodes` nodes, clustering starts until `reduceToMaxNumberOfNodes` nodes are left. This is done to ensure performance is continuously fluid.
reduceToNodes | Number | 300 | While zooming in and out, clusters can open up. Once there are more than `absoluteMaxNumberOfNodes` nodes, clustering starts until `reduceToMaxNumberOfNodes` nodes are left. This is done to ensure performance is continiously fluid.
chainThreshold | Number | 0.4 | Because of the clustering methods used, long chains of nodes can be formed. To reduce these chains, this threshold is used. A `chainThreshold` of 0.4 means that no more than 40% of all nodes are allowed to be a chain node (two connections). If there are more, they are clustered together.
clusterEdgeThreshold | Number | 20 | This is the absolute edge length threshold in pixels. If the edge is smaller on screen (that means zooming out reduces this length) the node will be clustered. This is triggered when zooming out.
sectorThreshold | Integer | 50 | If a cluster larger than `sectorThreshold` is opened, a seperate instance called a sector, will be created. All the simulation of nodes outside of this instance will be paused. This is to maintain performance and clarity when examining large clusters. A sector is collapsed when zooming out far enough. Also, when opening a cluster, if this cluster is smaller than this value, it is fully unpacked.
screenSizeThreshold | Number | 0.2 | When zooming in, the clusters become bigger. A `screenSizeThreshold` of 0.2 means that if the width or height of this cluster becomes bigger than 20% of the width or height of the canvas, the cluster is opened. If a sector has been created, if the sector is smaller than 20%, we collapse this sector.
fontSizeMultiplier | Number | 4.0 | This parameter denotes the increase in fontSize of the cluster when a single node is added to it.
forceAmplification | Number | 0.6 | This factor is used to calculate the increase of the repulsive force of a cluster. It is calculated by the following formula: `repulsingForce *= 1 + (clusterSize * forceAmplification)`.
distanceAmplification | Number | 0.2 | This factor is used to calculate the increase in effective range of the repulsive force of the cluster. A larger cluster has a longer range. It is calculated by the following formula: `minDistance *= 1 + (clusterSize * distanceAmplification)`.
edgeGrowth | Number | 11 | This factor determines the elongation of edges connected to a cluster.
nodeScaling.width | Number | 10 | This factor determines how much the width of a cluster increases in pixels per added node.
nodeScaling.height | Number | 10 | This factor determines how much the height of a cluster increases in pixels per added node.
nodeScaling.radius | Number | 10 | This factor determines how much the radius of a cluster increases in pixels per added node.
activeAreaBoxSize | Number | 100 | Imagine a square with an edge length of `activeAreaBoxSize` pixels around your cursor. If a cluster is in this box as you zoom in, the cluster can be opened in a seperate sector. This is regardless of the zoom level.

### Navigation controls

Graph has a menu with navigation controls, which is disabled by default. It can be configured with the following settings.

    // simple use of navigation controls
    var options: {
      navigation: true
    }

    // advanced use of navigation controls
    var options: {
      navigation: {
        iconPath: '/path/to/navigation/icons/'
      }
    }

Name | Type | Default | Description
--- | --- | --- | ---
iconPath | string | "/img" | The path to the icon images can be defined here. If custom icons are used, they have to have the same filename as the ones originally packaged with vis.js.

### Keyboard navigation

The graph can be navigated using shortcut keys. It can be configured with the following user-configurable settings. The default state for the keyboard navigation is off. The predefined keys can be found in the example 20_navigation.html.

    // simple use of keyboard controls
    var options: {
        keyboard: true
    }

    // advanced configuration for keyboard controls
    var options: {
      keyboard: {
        speed: {
          x: 10,
          y: 10,
          zoom: 0.02
        }
      }
    }

Name | Type | Default | Description
--- | --- | --- | ---
speed.x | Number | 10 | This defines the speed of the camera movement in the x direction when using the keyboard navigation.
speed.y | Number | 10 | This defines the speed of the camera movement in the y direction when using the keyboard navigation.
speed.zoom | Number | 0.02 | This defines the zoomspeed when using the keyboard navigation.

## Methods

Graph supports the following methods.

Method | Return Type | Description
--- | --- | ---
getSelection() | Array of ids | Returns an array with the ids of the selected nodes. Returns an empty array if no nodes are selected. The selections are not ordered.
on(event, callback) | none | Create an event listener. The callback function is invoked every time the event is triggered. Avialable events: `select`. The callback function is invoked as `callback(properties)`, where `properties` is an object containing event specific properties. See section Events for more information.
off(event, callback) | none | Remove an event listener created before via function `on(event, callback)`. See section Events for more information.
redraw() | none | Redraw the graph. Useful when the layout of the webpage changed.
setData(data,[disableStart]) | none | Loads data. Parameter `data` is an object containing nodes, edges, and options. Parameters nodes, edges are an Array. Options is a name-value map and is optional. Parameter `disableStart` is an optional Boolean and can disable the start of the simulation that would begin at the end of this function by default.
setOptions(options) | none | Set options for the graph. The available options are described in the section Configuration Options.
setSelection(selection) | none | Select nodes. `selection` is an array with ids of nodes to be selected. The array `selection` can contain zero or multiple ids. Example usage: `graph.setSelection([3, 5]);` will select nodes with id 3 and 5.
setSize(width, height) | none | Parameters `width` and `height` are strings, containing a new size for the visualization. Size can be provided in pixels or in percentages.

## Events

Graph fires events after one or multiple nodes are selected or deselected. The event can be catched by creating a listener.

Here an example on how to catch a `select` event.

    graph.on('select', function (properties) {
      alert('selected nodes: ' + properties.nodes);
    });

A listener can be removed via the function `off`:

    function onSelect (properties) {
      alert('selected nodes: ' + properties.nodes);
    }

    // add event listener
    graph.on('select', onSelect);

    // do stuff...

    // remove event listener
    graph.off('select', onSelect);

The following events are available.

name | Description | Properties
--- | --- | ---
select | Fired after the user selects or deselects a node by clicking it. Not fired when the method `setSelection`is executed. | `nodes`: an array with the ids of the selected nodes

## Data policy

All code and data is processed and rendered in the browser. No data is sent to any server.