9. The one or more computer storage devices of claim 8 , wherein the piecewise function is a spline function, and the plurality of connected segments correspond to a plurality of spline segments.
9. The one or more computer storage devices of claim 8 , wherein the piecewise function is a spline function, and the plurality of connected segments correspond to a plurality of spline segments. 10. The one or more computer storage devices of claim 9 , wherein the spline function is a cubic spline function.