Curves

A curve defines how to turn a discrete representation of a line as a sequence of points [[x₀, y₀], [x₁, y₁], [x₂, y₂], …] into a continuous path; i.e., how to interpolate between points. Curves are used by the line, area, and link marks, and are implemented by d3-shape.

Curve:

Fork

Plot.plot({
  marks: [
    Plot.lineY(numbers, {curve: "catmull-rom"}),
    Plot.dotY(numbers, {x: (d, i) => i})
  ]
})

The supported curve options are:

curve - the curve method, either a string or a function
tension - the curve tension (for fine-tuning)

The following named curve methods are supported:

basis - a cubic basis spline (repeating the end points)
basis-open - an open cubic basis spline
basis-closed - a closed cubic basis spline
bump-x - a Bézier curve with horizontal tangents
bump-y - a Bézier curve with vertical tangents
bundle - a straightened cubic basis spline (suitable for lines only, not areas)
cardinal - a cubic cardinal spline (with one-sided differences at the ends)
cardinal-open - an open cubic cardinal spline
cardinal-closed - an closed cubic cardinal spline
catmull-rom - a cubic Catmull–Rom spline (with one-sided differences at the ends)
catmull-rom-open - an open cubic Catmull–Rom spline
catmull-rom-closed - a closed cubic Catmull–Rom spline
linear - a piecewise linear curve (i.e., straight line segments)
linear-closed - a closed piecewise linear curve (i.e., straight line segments)
monotone-x - a cubic spline that preserves monotonicity in x
monotone-y - a cubic spline that preserves monotonicity in y
natural - a natural cubic spline
step - a piecewise constant function where y changes at the midpoint of x
step-after - a piecewise constant function where y changes after x
step-before - a piecewise constant function where x changes after y
auto - like linear, but use the (possibly spherical) projection, if any ^0.6.1

If curve is a function, it will be invoked with a given context in the same fashion as a D3 curve factory. The auto curve is only available for the line mark and link mark and is typically used in conjunction with a spherical projection to interpolate along geodesics.

The tension option only has an effect on bundle, cardinal and Catmull–Rom splines (bundle, cardinal, cardinal-open, cardinal-closed, catmull-rom, catmull-rom-open, and catmull-rom-closed). For bundle splines, it corresponds to beta; for cardinal splines, tension; for Catmull–Rom splines, alpha.

Curves ​

Curves