arc.endAngle([angle]) If angle is specified, sets the end angle to the specified function or number and returns this arc generator. If angle is not specified, returns the current end angle accessor, which defaults to: function endAngle(d) { return d.endAngle; } The angle is specified in radians, with 0 at -y (12 o’clock) and positive angles proceeding clockwise. If |endAngle - startAngle| ≥ τ, a complete circle or annulus is generated rather than a sector.

arc.cornerRadius([radius]) If radius is specified, sets the corner radius to the specified function or number and returns this arc generator. If radius is not specified, returns the current corner radius accessor, which defaults to: function cornerRadius() { return 0; } If the corner radius is greater than zero, the corners of the arc are rounded using circles of the given radius. For a circular sector, the two outer corners are rounded; for an annular sector, all four corners are rounded.

arc.context([context]) If context is specified, sets the context and returns this arc generator. If context is not specified, returns the current context, which defaults to null. If the context is not null, then the generated arc is rendered to this context as a sequence of path method calls. Otherwise, a path data string representing the generated arc is returned.

arc.centroid(arguments…) Computes the midpoint [x, y] of the center line of the arc that would be generated 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 + endAngle) / 2 and (innerRadius + outerRadius) / 2. For example:

arc(arguments…) 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: var 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 a

airy.radius([radius]) Defaults to 90°.