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# d3-shape Visualizations typically consist of discrete graphical marks, such as [symbols](#symbols), [arcs](#arcs), [lines](#lines) and [areas](#areas). While the rectangles of a bar chart may be easy enough to generate directly using [SVG](http://www.w3.org/TR/SVG/paths.html#PathData) or [Canvas](http://www.w3.org/TR/2dcontext/#canvaspathmethods), other shapes are complex, such as rounded annular sectors and centripetal Catmull–Rom splines. This module provides a variety of shape generators for your convenience. As with other aspects of D3, these shapes are driven by data: each shape generator exposes accessors that control how the input data are mapped to a visual representation. For example, you might define a line generator for a time series by [scaling](https://github.com/d3/d3-scale) fields of your data to fit the chart: ```js const line = d3.line() .x(d => x(d.date)) .y(d => y(d.value)); ``` This line generator can then be used to compute the `d` attribute of an SVG path element: ```js path.datum(data).attr("d", line); ``` Or you can use it to render to a Canvas 2D context: ```js line.context(context)(data); ``` For more, read [Introducing d3-shape](https://medium.com/@mbostock/introducing-d3-shape-73f8367e6d12). ## Installing If you use NPM, `npm install d3-shape`. Otherwise, download the [latest release](https://github.com/d3/d3-shape/releases/latest). You can also load directly from [d3js.org](https://d3js.org), either as a [standalone library](https://d3js.org/d3-shape.v2.min.js) or as part of [D3](https://github.com/d3/d3). AMD, CommonJS, and vanilla environments are supported. In vanilla, a `d3` global is exported: ```html <script src="https://d3js.org/d3-path.v2.min.js"></script> <script src="https://d3js.org/d3-shape.v2.min.js"></script> <script> const line = d3.line(); </script> ``` ## API Reference * [Arcs](#arcs) * [Pies](#pies) * [Lines](#lines) * [Areas](#areas) * [Curves](#curves) * [Custom Curves](#custom-curves) * [Links](#links) * [Symbols](#symbols) * [Custom Symbol Types](#custom-symbol-types) * [Stacks](#stacks) Note: all the methods that accept arrays also accept iterables and convert them to arrays internally. ### Arcs [<img alt="Pie Chart" src="https://raw.githubusercontent.com/d3/d3-shape/master/img/pie.png" width="295" height="295">](http://bl.ocks.org/mbostock/8878e7fd82034f1d63cf)[<img alt="Donut Chart" src="https://raw.githubusercontent.com/d3/d3-shape/master/img/donut.png" width="295" height="295">](http://bl.ocks.org/mbostock/2394b23da1994fc202e1) The arc generator produces a [circular](https://en.wikipedia.org/wiki/Circular_sector) or [annular](https://en.wikipedia.org/wiki/Annulus_\(mathematics\)) sector, as in a pie or donut chart. If the difference between the [start](#arc_startAngle) and [end](#arc_endAngle) angles (the *angular span*) is greater than [τ](https://en.wikipedia.org/wiki/Turn_\(geometry\)#Tau_proposal), the arc generator will produce a complete circle or annulus. If it is less than τ, arcs may have [rounded corners](#arc_cornerRadius) and [angular padding](#arc_padAngle). Arcs are always centered at ⟨0,0⟩; use a transform (see: [SVG](http://www.w3.org/TR/SVG/coords.html#TransformAttribute), [Canvas](http://www.w3.org/TR/2dcontext/#transformations)) to move the arc to a different position. See also the [pie generator](#pies), which computes the necessary angles to represent an array of data as a pie or donut chart; these angles can then be passed to an arc generator. <a name="arc" href="#arc">#</a> d3.<b>arc</b>() · [Source](https://github.com/d3/d3-shape/blob/master/src/arc.js) Constructs a new arc generator with the default settings. <a name="_arc" href="#_arc">#</a> <i>arc</i>(<i>arguments…</i>) · [Source](https://github.com/d3/d3-shape/blob/master/src/arc.js) Generates an arc for the given *arguments*. The *arguments* are arbitrary; they are simply propagated to the arc generator’s accessor functions along with the `this` object. For example, with the default settings, an object with radii and angles is expected: ```js const arc = d3.arc(); arc({ innerRadius: 0, outerRadius: 100, startAngle: 0, endAngle: Math.PI / 2 }); // "M0,-100A100,100,0,0,1,100,0L0,0Z" ``` If the radii and angles are instead defined as constants, you can generate an arc without any arguments: ```js const arc = d3.arc() .innerRadius(0) .outerRadius(100) .startAngle(0) .endAngle(Math.PI / 2); arc(); // "M0,-100A100,100,0,0,1,100,0L0,0Z" ``` If the arc generator has a [context](#arc_context), then the arc is rendered to this context as a sequence of [path method](http://www.w3.org/TR/2dcontext/#canvaspathmethods) calls and this function returns void. Otherwise, a [path data](http://www.w3.org/TR/SVG/paths.html#PathData) string is returned. <a name="arc_centroid" href="#arc_centroid">#</a> <i>arc</i>.<b>centroid</b>(<i>arguments…</i>) · [Source](https://github.com/d3/d3-shape/blob/master/src/arc.js) Computes the midpoint [*x*, *y*] of the center line of the arc that would be [generated](#_arc) by the given *arguments*. The *arguments* are arbitrary; they are simply propagated to the arc generator’s accessor functions along with the `this` object. To be consistent with the generated arc, the accessors must be deterministic, *i.e.*, return the same value given the same arguments. The midpoint is defined as ([startAngle](#arc_startAngle) + [endAngle](#arc_endAngle)) / 2 and ([innerRadius](#arc_innerRadius) + [outerRadius](#arc_outerRadius)) / 2. For example: [<img alt="Circular Sector Centroids" src="https://raw.githubusercontent.com/d3/d3-shape/master/img/centroid-circular-sector.png" width="250" height="250">](http://bl.ocks.org/mbostock/9b5a2fd1ce1a146f27e4)[<img alt="Annular Sector Centroids" src="https://raw.githubusercontent.com/d3/d3-shape/master/img/centroid-annular-sector.png" width="250" height="250">](http://bl.ocks.org/mbostock/c274877f647361f3df7d) Note that this is **not the geometric center** of the arc, which may be outside the arc; this method is merely a convenience for positioning labels. <a name="arc_innerRadius" href="#arc_innerRadius">#</a> <i>arc</i>.<b>innerRadius</b>([<i>radius</i>]) · [Source](https://github.com/d3/d3-shape/blob/master/src/arc.js) If *radius* is specified, sets the inner radius to the specified function or number and returns this arc generator. If *radius* is not specified, returns the current inner radius accessor, which defaults to: ```js function innerRadius(d) { return d.innerRadius; } ``` Specifying the inner radius as a function is useful for constructing a stacked polar bar chart, often in conjunction with a [sqrt scale](https://github.com/d3/d3-scale#sqrt). More commonly, a constant inner radius is used for a donut or pie chart. If the outer radius is smaller than the inner radius, the inner and outer radii are swapped. A negative value is treated as zero. <a name="arc_outerRadius" href="#arc_outerRadius">#</a> <i>arc</i>.<b>outerRadius</b>([<i>radius</i>]) · [Source](https://github.com/d3/d3-shape/blob/master/src/arc.js) If *radius* is specified, sets the outer radius to the specified function or number and returns this arc generator. If *radius* is not specified, returns the current outer radius accessor, which defaults to: ```js function outerRadius(d) { return d.outerRadius; } ``` Specifying the outer radius as a function is useful for constructing a coxcomb or polar bar chart, often in conjunction with a [sqrt scale](https://github.com/d3/d3-scale#sqrt). More commonly, a constant outer radius is used for a pie or donut chart. If the outer radius is smaller than the inner radius, the inner and outer radii are swapped. A negative value is treated as zero. <a name="arc_cornerRadius" href="#arc_cornerRadius">#</a> <i>arc</i>.<b>cornerRadius</b>([<i>radius</i>]) · [Source](https://github.com/d3/d3-shape/blob/master/src/arc.js) If *radius* is specified, sets the corner radius