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Sankey Diagram

This chart type belongs to PowerCharts XT

Sankey Diagram is a type of flow diagram that depicts the flow of resources (material, energy, cost, etc.) from one node to another. The start and endpoints of each flow are called nodes and the flow paths between them are called links. There can only be one link between a pair of nodes. The value of the flow between each pair of nodes is encoded by the width of the link. The coloration of the links help establish visual mapping with their respective nodes.

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To create a sankey diagram follow the steps given below:

  • In the JSON data, set the attributes and their corresponding values in "<attributeName>": "<value>" format.

  • Specify the chart type using the type attribute. To render a sankey diagram, set sankey.

  • Set the container object using renderAt attribute.

  • Specify the dimension of the chart using width and height attributes.

  • Set the type of data (JSON/XML) you want to pass to the chart object using dataFormat attribute.

For a detailed list of attributes, refer to the chart attributes page of sankey diagram.

A Sankey Diagram can be drawn in either a horizontal layout (default) or a vertical layout. A Sankey Diagram with horizontal orientation looks as shown below:

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There are 19 nodes in the Sankey Diagram provided above. A link connects any two nodes that are related to one another (i.e, a flow happens between them). If you hover over a node, you will see all the links (or relationships) associated with it. Hovering on a link will show both are nodes associated with it.

Sankey diagrams can be used to represent flow data. The flow happens from one node to another using a connecting link. No node should be repeated in the entire diagram and there should be at most one link between a pair of connecting nodes.

Some crucial concepts are briefed below:

Node

Nodes are crucial junctures in a flow diagram. Each node can have inflow and outflow of the flow resource. In our Sankey diagrams, they are currently represented by rectangles. A ton of customizations including size, color, label, padding, etc is possible.

Each node should occur only once in a Sankey diagram.

To customize the nodes, define 'nodes' object and specify the parameters for each node label.

Links are paths that connect the nodes. They give direction to the flow. They are fluid in nature and take shaped (or curve) based on the nodes which they connect. Each link should know it's source and sink nodes. The flow value is encoded by the width of the link. They can be customized in terms of color, curvature, and value.

If a link does not have a 'from' and 'to' node, it will not be drawn.

There should be the utmost one link between a pair of nodes.

Flow values

Each link in a Sankey Diagram represents flow from a source node to a target node. The direction of flow is left to right for a horizontal Sankey Diagram and top to bottom for a vertical diagram. The thickness of each link is dictated by the amount of flow from a source node to sink node. Cumulative flow values can be displayed on nodes.

Flow values are defined inside the link object by value parameter.

Salient Features

Orientation

The orientation of a Sankey Diagram can be either horizontal or vertical. To do so, set the value of the orientation attribute to horizontal or vertical respectively. By default, it is set to horizontal.

Use the code given below:

{
  "chart": {
    "orientation": "vertical";
  }
}

The chart will look as shown below:

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Click here to edit the above diagram.

No Node Sankey

If you set the value of the nodeWidth attribute to 0 under the chart object in a Sankey Diagram, the nodes are not rendered. The resultant chart only displays the links and is referred to as a No Node Sankey.

Use the code given below:

{
  "chart": {
    "nodeWidth": "0";
  }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

Blend Mode

The Sankey Diagram supports a blend mode for link colors. To apply this mode, you need to set the value of the linkColor attribute to blend. When you do that, a gradient formed by the combination of the colors of the source and target nodes is applied to the link. You can mention this under the chart object to apply the blend mode to every link in a chart. Otherwise, you can mention it under the links object to apply it to a particular link.

Use the code given below:

{
  "chart": {
    "linkColor": "blend";
  }
}

The chart will look as shown below:

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Click here to edit the chart.

Drag

You can drag a node in a Sankey Diagram in a vertical direction for horizontal Sankey and horizontal direction for vertical Sankey. By default, the drag feature is enabled for the Sankey diagram. To disable the drag, set the value of the enableDrag attribute to 0.

Use the code given below:

{
    "chart": {
        "enableDrag": "0"
    }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

You can set the angle in which links in a chart are rendered. To do so, set the value of the linkCurvature attribute to 0, 1, or any decimal value between them. Note that if you set the value to 0, the link will be rendered as a straight line, and if you set it to 1 it will be rendered with the maximum possible curvature.

You can set the curvature of all links globally in a chart. To do so, set the value of the linkCurvature attribute as mentioned above, and include it within the chart object. However, if you want to set the curvature of a single link, set the value of the curvature attribute as mentioned above, and include it within the links object for that particular link.

If you set the curvature of a link both globally (under chart object) and locally (under link object), the local value will override the global value.

Refer to the code given below:

{
    "chart": {
        "linkCurvature": "0"
    }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

Customizations of a Sankey Diagram

In the following sections, you will see the options for customizing nodes and links in a Sankey Diagram.

Node Customizations

Set Node Width

You can set the width of nodes across the chart. To do so, set the value of the nodeWidth attribute to the desired value.

Use the code given below:

{
  "chart": {
    "nodeWidth": "5";
  }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

Position Node Label

You can position a node label at the start, in the end, or inside a node. To do so, set the value of the nodeLabelPosition attribute to one of the following:

  • Set it to start, to position it to the left side of the node.

  • Set it to right, to position it to the right side of the node.

By default, the value of nodeLabelPosition is set to end.

You can position the node labels of the Sankey diagram only when the value of showNodeLabels value attribute is set to 1. The default of this attribute is 1.

Use the code given below:

{
    "chart": {
        "nodeLabelPosition": "right"
    }
}

The chart will look as shown below:

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Click here to edit the above diagram.

Hide Node Labels

If the labels of the node create clutter in your Sankey diagram, FusionCharts allows you to hide all the labels in the chart. To do so, set the showNodeLabels attribute to 0.

Refer to the code below:

{
    "chart": {
        "showNodeLabels": "0"
    }
}

The chart looks like as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

To hide the specific label of a node, set the value of showLabel attribute to 0. The showLabel attribute should be called inside nodes array.

Refer to the code below:

{
    "chart": { },
    "nodes": [{
        "label": "Netherlands",
        "showLabel": "0" //Disable Label of a particular node
    }]
}

The chart will look as shown below:

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Click here to edit the above diagram.

Show Node Values

To display the node values in the chart, set the value of the showNodeValues attribute to 1. By default, its value is set to 0.

Use the code given below:

{
    "chart": {
        "showNodeValues": "1"
    }
}

The chart will look as shown below:

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Click here to edit the above diagram.

To display the value for any specific node in the diagram, set the value of showValue attribute under nodes array.

Rotate Node Labels

You can rotate node labels to a vertical position instead of the default horizontal position. To do so, set the value of the rotateNodeLabels attribute to 1. By default, its value is set to 0.

Use the code given below:

{
    "chart": {
        "rotateNodeLabels": "1"
    }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

Set Padding between Nodes

You can add white space between consecutive nodes to make the chart look less cluttered. It will increase the vertical space between two consecutive nodes in a horizontal Sankey, and horizontal space between two nodes in a vertical Sankey.

You can add white space between consecutive nodes to make the chart look less cluttered. To do so, set the value of the nodeSpacing attribute to the desired value

Use the code given below:

{
    "chart": {
        "nodeSpacing": "10"
    }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

Configure Node Relaxation

You can drag a node in a Sankey Diagram away from other nodes, to draw attention to it. In a horizontal Sankey Diagram, you can drag nodes in a vertical direction. In a vertical Sankey Diagram, you can drag nodes in a horizontal direction. By default, the Sankey Diagram will reposition nodes and introduce some space between them if necessary, to avoid overlapping. This behavior is controlled by the nodeRelaxation attribute. By default, the value of the attribute is set to 1.

You can disable this behavior by setting the value of the nodeRelaxation attribute to 0.

Use the code given below:

{
    "chart": {
        "nodeRelaxation": "0"
    }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

Node Cosmetics

You can apply the following customizations to the appearance of a node.

Define the nodes array to specify the node cosmetics at individual node level.

Set Node Color

You can set the color of all nodes, across the Sankey Diagram. To do so, set the value of the nodeColor attribute to the hexadecimal value of the desired color, and include it within the chart object. However, if you want to set the color of a single node, set the value of the color attribute to the hex code of the desired color and include it within the nodes object for that particular node.

If you set the color of a node both globally (under chart object) and locally (under node object), the local value will override the global value.

Refer to the code given below:

{
    "chart": {
        "nodeColor": "#FFA816" //Applied to all the nodes in the diagram
    },
    "nodes": [{
        "label": "China",
        "color": "#ff0000" //Applied only to node of China
    }]
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

In the above chart, you can see that all nodes are of same color, except China's color which has been set locally.

Set Node Transparency

You can set the transparency of all nodes globally in a chart. To do so, set the value of the nodeAlpha attribute between 0 (transparent) and 100 (opaque), and include it within the chart object. On the other hand, if you want to set the transparency of a single node, set the value of the alpha attribute between 0 (transparent) and 100 (opaque) and include it within the nodes object for that particular node.

Note: If you set the transparency of a node both globally (under chart object) and locally (under node object), the local value will override the global value.

Refer to the code given below:

{
    "chart": {
        "nodeAlpha": "50" //Applied to all the nodes in the diagram
    },
    "nodes": [{
        "label": "China",
        "alpha": "100" //Applied only to node of China
    }]
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

In the above chart, you can see that all nodes are opaque, except China for which the value of alpha is set to 100 locally.

Node Label Cosmetics

You can apply a series of cosmetic modifications to node labels. They are listed below:

  • Set the font of the node label text using the nodeLabelFont attribute.

  • Set the color of the node label text using the nodeLabelFontColor attribute.

  • Set the transparency (between 0 for transparent and 100 for opaque) of the node label using the nodeLabelAlpha attribute.

  • Set the background color of the node label using the nodeLabelBgColor attribute.

  • Set the border color of the node label using the nodeLabelBorderColor attribute.

  • Set the border thickness of the node label using the nodeLabelBorderColor attribute.

  • Set the font size of the node label text using the nodeLabelFontSize attribute.

  • Set the font style of the node label text to bold using the nodeLabelFontBold attribute.

  • Set the font style of the node label text to italic using the nodeLabelFontItalic attribute.

  • Set the border radius of the node label using the nodeLabelBorderRadius attribute.

  • Set the space between the node label border and the node label using the nodeLabelBorderPadding attribute.

  • Set the node label border style to dashed using the nodeLabelBorderDashed attribute.

  • Set the lengths of node label border dashes using the nodeLabelBorderDashLen attribute. Note that this attribute only works if you apply the nodeLabelBorderDashed attribute to the node.

  • Set the length of the gaps between node label border dashes using the nodeLabelBorderDashGap attribute. Note that this attribute only works if you apply the nodeLabelBorderDashed attribute to the node.

  • Set the label to inherit its color from the node using the inheritLabelColorFromNode attribute.

Use the code given below to apply the customizations listed above to your chart:

{
    "chart": {
        "nodeLabelFont": "Arial",
        "nodeLabelFontColor": "#000fff",
        "nodeLabelAlpha": "50",
        "nodeLabelBgColor": "#ff0000",
        "nodeLabelBorderColor": "#000000",
        "nodeLabelFontSize": "13",
        "nodeLabelFontBold": "1",
        "nodeLabelFontItalic": "1",
        "nodeLabelBorderRadius": "5",
        "nodeLabelBorderPadding": "5",
        "nodeLabelBorderDashed": "1",
        "nodeLabelBorderDashLen": "3",
        "nodeLabelBorderDashGap": "2",
        "inheritLabelColorFromNode": "1"
    }
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

FusionCharts allows you to add straight links to your Sankey diagram instead of the default links. To do this, set the value of linkCurvature attribute to 0.

The default value of the linkCurvature attribute is 1.

Refer to the code below:

{
    "chart": {
        "linkCurvature": "0"
    }
}

A Sankey diagram with straight links look like as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

You can add white space between nodes and links to make the chart look less cluttered. To do this set the value of nodeLinkPadding in pixels.

Refer to the code below:

{
    "chart": {
        "nodeLinkPadding": "20"
    }
}

A Sankey diagram with 20 pixels of space between the node and the link looks like:

FusionCharts will load here..

Click here to edit the above diagram.

You can apply the following customizations to the appearance of a link.

You can customize the color of a link using the linkColorattribute. Set its value to one of the following options:

  • Set it to source to make the link inherit the color of its source node or the from node.

  • Set it to target to make the link inherit its color from the target node or the to node.

  • Set it to blend to combine the colors of the source and target nodes of a link and apply that to the link as a gradient.

  • Set it to the hexadecimal value of a color to apply that color to the link.

You can set the color of all links globally. To do so, set the value of the linkColor attribute to one of the options mentioned above, and include it within the chart object. However, if you want to set the color of a single link, set the value of the color attribute to one of the options given above and include it within the links object for that particular link.

If you set the color of a link both globally (under chart object) and locally (under link object), the local value will override the global value.

Refer to the code given below:

{
    "chart": {
        "linkColor": "#FFA817"
    },
    "links": [
        {
          "from": "Germany",
          "to": "European Union",
          "value": 1468990,
          "color": "#ff0000"
        }
    ]
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

In the above chart, you can see that all links are of same color, except the links from Germany to European Union which has been set locally.

You can set the transparency of all links globally in a chart. To do so, set the value of the linkAlpha attribute between 0 (transparent) and 100 (opaque), and include it within the chart object. However, if you want to set the transparency of a single link, set the value of the alpha attribute between 0 (transparent) and 100 (opaque) and include it within the link object for that particular link.

If you set the transparency of a link both globally (under chart object) and locally (under link object), the local value will override the global value.

Refer to the code given below:

{
    "chart": {
        "linkAlpha": "20"
    },
    "links": [
        {
          "from": "Germany",
          "to": "European Union",
          "value": 1468990,
          "alpha": "100"
        }
    ]
}

The chart will look as shown below:

FusionCharts will load here..

Click here to edit the above diagram.

In the above chart, you can see the transparency of all the links are set to 20 except for the link from Germany to European Union.