Sankey diagram

Sankey visualisation

Updated a year ago to v2.2.2 by Flourish team

How to use this template

Sankey diagram

A template for creating Sankey diagrams and alluvial diagrams. Ideal for displaying energy flows or the changes in seats between parties from before to after an election.

Data requirements

The template works with two types of data format:

  1. Flows are already in the data, and each row has a source name, target name and flow value (plus optional step from and step to columns for multistep alluvial diagrams).

  2. Flows are not already in the data. In this model, each row is a entity (e.g. a seat in an election), with a source name and target name (e.g. representing the ruling party before and after the election). With this kind of data the flows are computed automatically by adding up source–target pairs (taking into account step from and step to values).

Tips

  • If specifying flow values directly, the column used for Value of link must contain positive numbers or zero
  • Names are compared and values summed using case-insensitive comparisons with all non-alphanumeric characters stripped. For example “Cat“ and “cA ?t“ are considered identical.
  • Hovering over a link will defocus all other links and any node not connected to that link. Hovering over a node will defocus all links that are not directly connected to that node and all nodes not connected via a link to the hovered node. You can fix focus on a node or link and all its connections by clicking on the entity. This is particularly useful for guiding viewers through your stories. Click a focused node or link again to remove the focus or click any other node or link to change focus to that entity.
  • The optional Step from and Step to column selection boxes make it possible to construct multistep alluvial diagrams where links go from Step from to Step to along the horizontal direction. If only Step from is assigned to a column then the value of Step to is assumed to be one greater than that of Step from. Similarly, if only Step to is assigned to a column then the value of Step from is assumed to be one less than that of Step to.

This section documents API usage specific to this template, so for an introduction we suggest you refer to the generic API documentation instead.

template: @flourish/sankey

version: 2

Template data

There are two different formats in which you can supply data to this template. Which one will be more convenient for you likely depends on the source of your data, as described below.

Array of objects with arbitrary keys, and a bindings object

This format is most likely useful when you have data from an external source, such as CSV data loaded from d3-dsv. You should supply this attached to the opts.data, which might look like:

    {
        links: [
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            ...
        ]
    }

... but with the keys being the column headers from your source data instead. To tell the API how these values from each column should be associated with the keys that the template is expecting, you must also supply an object attached to opts.bindings. (The meanings of the keys in the bindings object are documented below.) The minimal bindings you can supply for this template are as shown in this example:

{
    template: "@flourish/sankey",
    version: "2",
    bindings: {
        links: {
            source: "LinksHeader1",
            target: "LinksHeader2"
        }
    },
    data: {
        links: [
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            ...
        ]
    }
}

All possible bindings that you can supply are shown in this example:

{
    template: "@flourish/sankey",
    version: "2",
    bindings: {
        links: {
            source: "LinksHeader1",
            target: "LinksHeader2",
            value: "LinksHeader3",
            step_from: "LinksHeader4",
            step_to: "LinksHeader5"
        }
    },
    data: {
        links: [
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            { "LinksHeader1": ..., "LinksHeader2": ..., ... },
            ...
        ]
    }
}

(As before, the keys containing "Header" would be replaced by column names from your data source.)

Array of objects with template-defined keys

There is an alternative format you can use, which is likely to be easier to use if your data is not from a spreadsheet source. With this alternative format you supply your data to the template as an array of objects, attached to opts.data, where the keys must be those used by the template, as documented below. In this case there is no need to supply a bindings object, since the key names are already those expected by the template. The required properties in the data object are as follows (scroll down for a description of what each property is):

{
template: "@flourish/sankey",
version: "2",
data: {
    links: [
        {
            source: ...,
            target: ...
        },
        ...
    ]
},
...
}

And the full list of all possible properties is as follows:

{
template: "@flourish/sankey",
version: "2",
data: {
    links: [
        {
            source: ...,
            target: ...,
            value: ...,
            step_from: ...,
            step_to: ...
        },
        ...
    ]
},
...
}

Meanings of the template data keys:

  • links.source: source
  • links.target: target
  • links.value: A numerical value used to set the thickness of the links.
  • links.step_from: An integer value used to indicate where a link starts from (used only in Alluvial mode).
  • links.step_to: An integer value used to indicate where a link goes to (used only in Alluvial mode).

Template settings

Options for opts.state.

Layout

mode string

Mode.

Allowed values:

  • alluvial (Alluvial (stepwise composition))
  • sankey (Sankey (arbitrary flows))

iterations number

Iter.. Number of iterations of the layout algorithm before the diagram is drawn. The higher the value, the fewer link crossings you will see but the less likely the order is to match that in the datasheet.

Max: 100

spread string

Spread.

Allowed values:

  • step (Based on step values)
  • column (Evenly)

alignment string

Alignment.

Allowed values:

  • justify (Justify)
  • center (Centre)
  • left (Left)
  • right (Right)

node_width number

Node width.

Min: 2

Max: 50

node_padding number

Vertical node separation.

Max: 20

margin number

Margin. Maximum margin, may be less on small screens

Max: 50

bg_color color

Background colour.

max_width number

Maximum width. Leave blank to stretch to container width

colors.palette colors

Palette.

colors.extend boolean

Auto-extend. Automatically generate additional colours when needed to avoid the palette colours being used more than once. Added colours are based on the average lightness and chroma values of the palette. This works best if the palette’s colours do not have very high or low saturation.

colors.advanced boolean

Fine tune. Fine tune how additional colours are added to the palette.

colors.hue_rotation_angle number

Hue rotation for added colours. Angle, in degrees in HCL colourspace, between one generated colour and the next. The default value, ~360/(Golden ratio), ensures adjacent hues are not too similar.

Max: 360

colors.custom_palette text

Custom overrides. Type the name of the entity whose colour you want to set, a colon and then a colour (using a name, hex-code or rgb declaration). Multiple colours can be set using multiple lines. For example:<br /><hr />Party 1: red<br />Party 2: #4455AA<br />Party 3: rgb(30,168,26)

Link opacity.

Max: 1

background_opacity number

Defocused opacity. When a node or link is in focus, this sets the opacity of the others

Max: 1

Labels

label_mode string

Allowed values:

  • outwards (Favour outside)
  • inwards (Favour inside)

label_color_mode string

Text.

Allowed values:

  • none (None)
  • auto (Auto)
  • fixed (Fixed)

label_color color

 .

label_outline_color_mode string

Outline.

Allowed values:

  • none (None)
  • auto (Auto)
  • fixed (Fixed)

label_outline_color color

 .

label_responsive boolean

Sizing. Auto changed the label size based on the window size, subject to the specified min and max

Allowed values:

  • true (Auto)
  • false (Fixed)

label_font_size number

In pixels.

label_font_size_min number

Min.

label_font_size_max number

Max.

label_bold boolean

Bold.

label_show_values boolean

Show node values.

Allowed values:

  • true (None)
  • false (All)

Show link values.

Allowed values:

  • never (None)
  • focused (Focused)
  • always (All)

Colour.

Number formatting

localization.input_decimal_separator string

Decimal separator in data sheet. Used for interpreting your data. Only change if data is not displaying on the chart as expected.

Allowed values:

  • . (.)
  • , (,)

localization.output_separators string

Number format to display. How the numbers should appear on chart labels

Allowed values:

  • ,. (12,235.67)
  • ., (12.345,67)
  • . (12235.67)
  • , (12345,67)
  • . (12 235.67)
  • , (12 345,67)

formatting.prefix string

Prefix. Text to place in front of number

formatting.suffix string

Suffix. Text to place after number

formatting.n_dec number

Decimal places. Use negative integers to round to positive powers of ten (eg -2 rounds to the nearest 100)

Min: -10

Max: 10

formatting.strip_zeros boolean

Remove trailing zeros.

formatting.strip_separator boolean

Hide thousands separator below 10,000. Turn off if you want four-digit numbers to include a separator, e.g. “1,234” rather than “1234”.

formatting.transform_labels boolean

Multiply/divide values.

formatting.transform string

Allowed values:

  • multiply (Multiply by)
  • divide (Divide by)
  • exponentiate (×10 to the power of)

formatting.multiply_divide_constant number

formatting.exponentiate_constant number

header.title string

Title.

header.subtitle string

Subtitle.

header.color color

Color.

header.align string

Alignment.

Allowed values:

  • left (fa-align-left)
  • center (fa-align-center)
  • right (fa-align-right)

header.margin number

Margin.

header.margin_advanced boolean

Advanced margin settings.

header.margin_top number

Top.

header.margin_right number

Right.

header.margin_bottom number

Bottom.

header.margin_left number

Left.

footer.source_name string

Source name.

footer.source_url string

Source url.

footer.multiple_sources boolean

Multiple sources.

footer.source_name_2 string

Source name.

footer.source_url_2 string

Source url.

footer.source_name_3 string

Source name.

footer.source_url_3 string

Source url.

footer.source_label string

Source label.

footer.note string

Note.

footer.size number

Size.

footer.color color

Color.

footer.align string

Alignment.

Allowed values:

  • left (fa-align-left)
  • center (fa-align-center)
  • right (fa-align-right)

footer.margin number

Overall.

footer.margin_top number

Top.

footer.margin_right number

Right.

footer.margin_bottom number

Bottom.

footer.margin_left number

Left.

footer.margin_advanced boolean

Advanced.