# backSpline

0th

Percentile

##### 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 or npolySpline. That is, the object must represent a natural interpolation spline but it can be either in the B-spline 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.

interpSpline
library(splines) # NOT RUN { 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 ) # }