d3.interpolateArray()

d3.interpolateArray(a, b)

Returns an interpolator between the two arrays a and b. Internally, an array template is created that is the same length in b. For each element in b, if there exists a corresponding element in a, a generic interpolator is created for the two elements using interpolate. If there is no such element, the static value from b is used in the template. Then, for the given parameter t, the template’s embedded interpolators are evaluated. The updated array template is then returned.

For example, if a is the array [0, 1] and b is the array [1, 10, 100], then the result of the interpolator for t = 0.5 is the array [0.5, 5.5, 100].

Note: no defensive copy of the template array is created; modifications of the returned array may adversely affect subsequent evaluation of the interpolator. No copy is made for performance reasons; interpolators are often part of the inner loop of animated transitions.