d3.geoLength(feature) Returns the great-arc length of the specified GeoJSON feature in radians. For polygons, returns the perimeter of the exterior ring plus that of any interior rings.

d3.curveMonotoneY(context) Produces a cubic spline that preserves monotonicity in x, assuming monotonicity in y, as proposed by Steffen in A simple method for monotonic interpolation in one dimension: “a smooth curve with continuous first-order derivatives that passes through any given set of data points without spurious oscillations. Local extrema can occur only at grid points where they are given by the data, but not in between two adjacent grid points.”

d3.timeThursdays(start, stop[, step]) d3.utcThursdays(start, stop[, step]) Aliases for timeThursday.range and utcThursday.range.

quantile.copy() Returns an exact copy of this scale. Changes to this scale will not affect the returned scale, and vice versa.

area.x([x]) If x is specified, sets x0 to x and x1 to null and returns this area generator. If x is not specified, returns the current x0 accessor.

rotation.invert(point) Returns a new array [longitude, latitude] in degrees representing the point of the given rotated point; the inverse of rotation. The point must be specified as a two-element array [longitude, latitude] in degrees.

radialArea.defined([defined]) Equivalent to area.defined.

stack.offset([offset]) If offset is specified, sets the offset accessor to the specified function or array and returns this stack generator. If offset is not specified, returns the current offset acccesor, which defaults to stackOffsetNone; this uses a zero baseline. See stack offsets for the built-in offsets. If offset is a function, it is passed the generated series array and the order index array. The offset function is then responsible for updating the lower and upper values in the serie

d3.interpolateCubehelixDefault(t) Given a number t in the range [0,1], returns the corresponding color from Green’s default Cubehelix represented as an RGB string.

d3.scalePoint() Constructs a new point scale with the empty domain, the unit range [0, 1], no padding, no rounding and center alignment.