backSpline {splines} | R Documentation |

## Monotone Inverse Spline

### Description

Create a monotone inverse of a monotone natural spline.

### Usage

```
backSpline(object)
```

### Arguments

`object` |
an object that inherits from class |

### 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.

### Author(s)

Douglas Bates and Bill Venables

### See Also

### Examples

```
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 )
```

*splines*version 4.4.1 Index]