backSpline
Monotone Inverse Spline
Create a monotone inverse of a monotone natural spline.
 Keywords
 models
Usage
backSpline(object)
Arguments
 object
 an object that inherits from class
nbSpline
ornpolySpline
. That is, the object must represent a natural interpolation spline but it can be either in the Bspline representation or the piecewise polynomial one. The spline is checked to see if it represents a monotone function.
Value

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.
See Also
Examples
library(splines)
require(graphics)
ispl < interpSpline( women$height, women$weight )
bspl < backSpline( ispl )
plot( bspl ) # plots over the range of the knots
points( women$weight, women$height )
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