Data interpolation makes a big difference to how charts renders. Here are all of the built-in interpolations of D3.

**linear** - piecewise linear segments, as in a polyline.

**linear-closed** - close the linear segments to form a polygon.

**step** - alternate between horizontal and vertical segments, as in a step function.

**step-before** - alternate between vertical and horizontal segments, as in a step function.

**step-after** - alternate between horizontal and vertical segments, as in a step function.

**basis** - a B-spline, with control point duplication on the ends.

**basis-open** - an open B-spline; may not intersect the start or end.

**basis-closed** - a closed B-spline, as in a loop.

**bundle** - equivalent to basis, except the tension parameter is used to straighten the spline.

**cardinal** - a Cardinal spline, with control point duplication on the ends.

**cardinal-open** - an open Cardinal spline; may not intersect the start or end, but will intersect other control points.

**cardinal-closed** - a closed Cardinal spline, as in a loop.

**monotone** - cubic interpolation that preserves monotonicity in y.