cpplot {locfit} | R Documentation |

## Compute a Cp plot.

### Description

The `cpplot`

function loops through calls to the `cp`

function (and hence to `link{locfit}`

), using a different
smoothing parameter for each call.
The returned structure contains the Cp statistic for each fit, and can
be used to produce an AIC plot.

### Usage

cpplot(..., alpha, sig2)

### Arguments

`...` |
arguments to the `cp` , `locfit`
functions. |

`alpha` |
Matrix of smoothing parameters. The `cpplot` function
loops through calls to `cp` , using each row of
`alpha` as the smoothing parameter in turn. If `alpha`
is provided as a vector, it will be converted to a one-column
matrix, thus interpreting each component as a nearest neighbor
smoothing parameter. |

`sig2` |
Residual variance. If not specified, the residual variance
is computed using the fitted model with the fewest residual degrees
of freedom. |

### Value

An object with class `"gcvplot"`

, containing the smoothing
parameters and CP scores. The actual plot is produced using
`plot.gcvplot`

.

### See Also

`locfit`

,
`locfit.raw`

,
`gcv`

,
`aic`

,
`plot.gcvplot`

### Examples

data(ethanol)
plot(cpplot(NOx~E,data=ethanol,alpha=seq(0.2,1.0,by=0.05)))

[Package

*locfit* version 1.1-9

Index]