interpSpline {splines} | R Documentation |

## Create an Interpolation Spline

### Description

Create an interpolation spline, either from `x`

and `y`

vectors, or from a formula/data.frame combination.

### Usage

interpSpline(obj1, obj2, bSpline = FALSE, period = NULL,
na.action = na.fail)

### Arguments

`obj1` |
Either a numeric vector of `x` values or a formula. |

`obj2` |
If `obj1` is numeric this should be a numeric vector
of the same length. If `obj1` is a formula this can be an
optional data frame in which to evaluate the names in the formula. |

`bSpline` |
If `TRUE` the b-spline representation is returned,
otherwise the piecewise polynomial representation is returned.
Defaults to `FALSE` . |

`period` |
An optional positive numeric value giving a period for a
periodic interpolation spline. |

`na.action` |
a optional function which indicates what should happen
when the data contain `NA` s. The default action
(`na.omit` ) is to omit any incomplete observations. The
alternative action `na.fail` causes `interpSpline` to print
an error message and terminate if there are any incomplete
observations. |

### Value

An object that inherits from class `spline`

. The object can be in
the B-spline representation, in which case it will be of class
`nbSpline`

for natural B-spline, or in the piecewise polynomial
representation, in which case it will be of class `npolySpline`

.

### Author(s)

Douglas Bates and Bill Venables

### See Also

`splineKnots`

,
`splineOrder`

,
`periodicSpline`

.

### Examples

ispl <- interpSpline( women$height, women$weight )
ispl2 <- interpSpline( weight ~ height, women )
# ispl and ispl2 should be the same
plot( predict( ispl, seq( 55, 75, len = 51 ) ), type = "l" )
points( women$height, women$weight )
plot( ispl ) # plots over the range of the knots
points( women$height, women$weight )
splineKnots( ispl )

[Package

*splines* version 2.1.0

Index]