Create a monotone inverse of a monotone natural spline.
an object that inherits from class
An object of class
polySpline that contains the piecewise
polynomial representation of a function that has the appropriate
values and derivatives at the knot positions to be an inverse of the
spline represented by
object. Technically this object is not a
spline because the second derivative is not constrained to be
continuous at the knot positions. However, it is often a much better
approximation to the inverse than fitting an interpolation spline to
the y/x pairs.
Douglas Bates and Bill Venables
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