\Header{backSpline}{Monotone Inverse Spline}
\alias{backSpline.nbSpline}{backSpline}
\alias{backSpline.npolySpline}{backSpline}
\keyword{models }{backSpline}
\begin{Usage}
\begin{verbatim}
backSpline(object)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\texttt{object}] An object that inherits from class \texttt{nbSpline} or
\texttt{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 representation. 
The spline is checked to see if represents a monotone function.

\end{ldescription}
\end{Arguments}
\begin{Description}
Create a monotone inverse of a monotone natural spline.\end{Description}
\begin{Value}
An object of class \texttt{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 \texttt{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.\end{Value}
\begin{Author}
Douglas Bates and Bill Venables\end{Author}
\begin{SeeAlso}
\texttt{\Link{interpSpline}}\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
data( women )
ispl <- interpSpline( women$height, women$weight )
bspl <- backSpline( ispl )
plot( bspl )    # plots over the range of the knots
\end{ExampleCode}
\end{Examples}

