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Sankey

Creates a Sankey visualization based on a defined set of nodes and links.

Basic example

Section titled “Basic example”

Supplying only links lets the layout infer every node from the source/target ids and route the flows between them.

const config = {
  links: [
    {source: "alpha", target: "beta"},
    {source: "alpha", target: "gamma"},
    {source: "beta", target: "delta"},
    {source: "beta", target: "epsilon"},
    {source: "zeta", target: "gamma"},
    {source: "theta", target: "gamma"},
    {source: "eta", target: "gamma"},
  ],
};
Section titled “Data driven link width”

Each link’s value sets its thickness, so flows are weighted by magnitude.

The value of each link, which sets its width: a key or an accessor function that receives the link and its index. Defaults to 1 for every link.

Node spacing

Section titled “Node spacing”

nodeWidth sets how thick each node bar is drawn and nodePadding the vertical gap between nodes in a column—raise nodePadding to spread crowded columns apart.

const config = {
  links: [
    {source: "alpha", target: "beta"},
    {source: "alpha", target: "gamma"},
    {source: "beta", target: "delta"},
    {source: "beta", target: "epsilon"},
    {source: "gamma", target: "delta"},
  ],
  nodeWidth: 30,
  nodePadding: 40,
};

Directional arrows

Section titled “Directional arrows”

arrows adds an arrowhead where each flow enters its target node, reinforcing the left-to-right direction. Use "both" for bi-directional flows or a per-link accessor.

Draws arrowheads on the links: true (or "target") where each link enters its target, "source" where it leaves its source, "both", or false for none. Also accepts an accessor function returning one of those per link.

The arrowhead size in pixels, or an accessor function returning one per link. Defaults to the link's width, kept between 8 and 28.

Node labels

Section titled “Node labels”

Each node is labeled beside it, over its outgoing flows, or over its incoming flows in the last column. A node too thin for a line of text, like Geothermal here, goes unlabeled. label sets the text, shapeConfig.Rect.labelConfig styles it, and shapeConfig: {Rect: {label: false}} turns the labels off.

const config = {
  links: [
    {source: "Coal", target: "Electricity", value: 30},
    {source: "Natural Gas", target: "Electricity", value: 25},
    {source: "Natural Gas", target: "Industrial", value: 14},
    {source: "Nuclear", target: "Electricity", value: 18},
    {source: "Geothermal", target: "Electricity", value: 0.4},
    {source: "Petroleum", target: "Transportation", value: 35},
    {source: "Electricity", target: "Residential", value: 20},
    {source: "Electricity", target: "Commercial", value: 18},
    {source: "Electricity", target: "Industrial", value: 12},
    {source: "Residential", target: "Energy Services", value: 14},
    {source: "Residential", target: "Rejected Energy", value: 6},
    {source: "Commercial", target: "Energy Services", value: 12},
    {source: "Commercial", target: "Rejected Energy", value: 6},
    {source: "Industrial", target: "Energy Services", value: 18},
    {source: "Industrial", target: "Rejected Energy", value: 8},
    {source: "Transportation", target: "Energy Services", value: 8},
    {source: "Transportation", target: "Rejected Energy", value: 27},
  ],
  value: "value",
  shapeConfig: {Rect: {labelConfig: {fontWeight: 600}}},
};

Configuration

import {Sankey} from "@d3plus/core";

Extends Viz.

activefalse | function

The active callback function for highlighting shapes.

arrowSizenumber | function

The arrowhead size in pixels, or an accessor function returning one per link. Defaults to the link's width, kept between 8 and 28.

arrowsboolean | "target" | "source" | "both" | functionDefault false

Draws arrowheads on the links: true (or "target") where each link enters its target, "source" where it leaves its source, "both", or false for none. Also accepts an accessor function returning one of those per link.

classNamestring | array.<string> | undefined

CSS classes added to the outermost element this chart or component draws into, next to its fixed d3plus classes, so page CSS can target it: a chart's root <svg class="d3plus-viz"> (its <canvas> with the Canvas renderer) and a standalone component's <svg>. Takes a space-separated string or an array. A new value replaces the classes the previous one added; unset adds none. Tooltips take their own tooltipConfig.className.

colorDefaultscolordefaultsconfig

Overrides the default colors used when assigning fills from data and choosing legible text colors: dark and light (the text colors picked for contrast against a background), missing (null/undefined values), on/off (true/false values), sequential (the anchor hue for magnitude ramps), and scale (the categorical palette, given as a d3 ordinal scale or an array of colors). Keys are merged into the current defaults, and a Viz passes its overrides down to the shapes and components it draws.

configd3plusconfig

Methods that correspond to the key/value pairs and returns this class.

datastring | array.&lt;datapoint&gt; | object

The primary data array used to draw the visualization. The value passed should be an Array of objects or a String representing a filepath or URL to be loaded. The following filetypes are supported: csv, tsv, txt, and json.

If your data URL needs specific headers to be set, an Object with a "url" and "headers" (or any other fetch request option) may also be passed. An Object with any other key is a data row, not a request.

Additionally, a custom formatting function can be passed as a second argument to this method. This custom function will be passed the data that has been loaded, as long as there are no errors. This function should return the final array of obejcts to be used as the primary data array. For example, some JSON APIs return the headers split from the data values to save bandwidth. These would need be joined using a custom formatter.

If you would like to specify certain configuration options based on the yet-to-be-loaded data, you can also return a full config object from the data formatter (including the new data array as a key in the object).

To re-fetch a URL on an interval and redraw when its data changes, set dataPollingInterval; each poll runs the same formatter.

Defaults to an empty array ([]).

facetstring | false | function

Splits the chart into small multiples: a grid of equally sized panels, one per distinct value of this data key or accessor, each drawing the chart for that value's rows. The panels share one legend, color scale, title, and timeline, color each series the same way, and hover, tooltips, and legend clicks apply across all of them. Pass false to draw a single chart. See facetConfig for the grid's layout and shared scales.

facetConfigfacetconfig

Configuration for small multiples (see facet), merged into the current config: - columns / rows: the grid's shape. Chosen by default to make the panels as large as the chart's shape allows. - padding: the space between panels, in pixels (default 20). - sort: panel order — "ascending" (default), "descending", "data" (first appearance), a comparator over facet values, or an Array of values. - scales: "shared" (default) gives every panel of a chart with axes the same x/y domains; "independent" fits each panel to its own rows. Funnel defaults to "independent" (each panel sized to its own widest stage); "shared" sizes every panel against the widest stage across all panels. PolarArea and RadialBar default to "independent" (each panel's rings and ticks fit its own values); "shared" gives every panel the same value domain. - axes: with shared scales, "outer" (default) labels the axes only along the grid's left and bottom edges; "all" labels every panel. An object sets each axis on its own, as in {x: "all", y: "outer"}: every panel labels its x axis, only the left column labels its y axis, and the panels' plot areas line up. BumpChart defaults to "all", and Marimekko labels its categories on every panel and its 0–100% share axis only along the outer edge, even with independent scales. - title: a (value, data) => string function for each panel's title, or false to hide panel titles. - titleConfig: TextBox config for the panel titles (fontSize, fontWeight, fontColor, textAnchor, padding, …).

fontFamilystring | array.&lt;string&gt;

The font family used throughout the visualization.

groupBystring | function | array.&lt;string | function&gt;

Defines the mapping between data and shape. The value can be a String matching a key in each data point (default is "id"), or an accessor Function that returns a unique value for each data point. Additionally, an Array of these values may be provided if the visualization supports nested hierarchies.

highlightfalse | function

Persistently emphasizes the data points matching the given predicate: the matching marks keep their color while every other mark is de-emphasized to a neutral gray (the "emphasis" form — highlight one series, gray the rest). Unlike hover/active (transient, opacity-based), highlight is a standing state that survives pointer movement. Pass false to clear it.

hoverfalse | function

The hover callback function for highlighting shapes on mouseover.

iterationsunknownDefault 6

The number of relaxation iterations d3-sankey runs to position the nodes (see its iterations).

linkSortfunction

A comparator that orders the links at each node, passed to d3-sankey's linkSort. When unset, links are ordered by the position of the node at their other end.

The flows between nodes. Each link's linksSource and linksTarget values match a node's nodeId, and its width comes from value. Accepts an array of links, or a URL/filepath string to load them from. An optional formatting function can be passed as a second argument; it receives the loaded data and returns the final links array.

linksSourceunknownDefault "source"

The key in each link object that holds its source node's id.

linksTargetunknownDefault "target"

The key in each link object that holds its target node's id.

localestring | object

The locale used for all text and number formatting. Supports the locales defined in d3plus-format. The locale can be a complex Object, a locale code (like "en-US"), or a 2-digit language code (like "en"). If a 2-digit code is provided, the "findLocale" function is used to identify the most approximate locale.

noDataMessagebooleanDefault false

Toggles the visibility of the status message that is displayed when no data is supplied to the visualization.

nodeAlign"justify" | "left" | "right" | "center" | functionDefault sankeyJustify

How nodes are aligned horizontally: "justify" (default), "left", "right", or "center", or a custom d3-sankey alignment function.

nodeIdstring | functionDefault "id"

The unique id of each node, as a key or an accessor function. Link sources and targets are matched against these ids.

nodePaddingunknownDefault 8

The vertical gap between nodes in the same column, in pixels.

nodeSortfunction

A comparator that orders the nodes in each column, passed to d3-sankey's nodeSort. When unset, d3-sankey orders them to reduce link crossings.

nodeWidthunknownDefault 30

The width of each node, in pixels.

nodesobject[] | stringDefault "nodes"

The nodes to draw. When empty, the nodes are the unique source and target values in links. Accepts an array of node objects, or a URL/filepath string to load them from. An optional formatting function can be passed as a second argument; it receives the loaded data and returns the final nodes array.

onstring

Event listener for the specified event typenames. Mirrors the core d3-selection behavior.

parentunknown

Parent config used by the wrapper.

renderfunction

Draws the visualization given the specified configuration.

rendererboolean | "svg" | "canvas"

Selects which @d3plus/render backend paints the visible output. "svg" = SvgRenderer (default), "canvas" = CanvasRenderer. Boolean arguments both normalize to "svg".

selectstring | htmlelement

The SVG container element as a d3 selector or DOM element. Defaults to undefined.

shapestring | functionDefault "Rect"

Changes the primary shape used to represent each data point in a visualization. Not all visualizations support changing shapes, this method can be provided the String name of a D3plus shape class (for example, "Rect" or "Circle"), or an accessor Function that returns the String class name to be used for each individual data point.

shapeConfigd3plusconfigDefault function

Configuration object with key/value pairs applied as method calls on each shape.

thresholdnumber | function

The threshold value for bucketing small data points together, as a share of the total. On a stacked Plot, the series whose summed value across every position is under that share of the whole chart's total merge into one series, stacked on top. A bucket needs at least two items, and its tooltips list them. Off (0) by default on Plot charts.

thresholdKeystring | function

Accessor for the value used in the threshold algorithm. A stacked Plot defaults to its stacked value.

timestring | false | function

Accessor function or string key for the time dimension of each data point.

timelineDefaultstring | date | array.&lt;string | date&gt;

The starting time or range for the timeline. Can be a single Date/String, or an Array of 2 values representing the min and max.

tooltipConfigtooltipconfig

Configuration for the tooltip component.

totalstring | boolean | function

Accessor function or string key for the total value displayed in the visualization.

translatefunction

Defines how informational text strings should be displayed. By default, this function will try to find the string in question (which is the first argument provided to this function) inside of an internally managed translation Object. If you'd like to override to use custom text, simply pass this method your own custom formatting function.

valuestring | functionDefault 1

The value of each link, which sets its width: a key or an accessor function that receives the link and its index. Defaults to 1 for every link.