d3.interpolateObject(a, b) Returns an interpolator between the two objects a and b. Internally, an

d3.interpolateBasis(values) Returns a uniform nonrational B-spline interpolator through the specified array of values

d3.interpolateHslLong(a, b)

d3.interpolateCubehelixLong(a, b)

d3.interpolateRgbBasisClosed(colors) Returns a uniform nonrational B-spline interpolator through the specified array of colors

d3.interpolateHsl(a, b)

d3.quantize(interpolator, n) Returns n uniformly-spaced samples from the specified interpolator, where

d3.interpolateRgb(a, b)

d3.interpolateRound(a, b) Returns an interpolator between the two numbers a and b; the interpolator

d3.interpolateHcl(a, b)