lf {locfit} | R Documentation |

This function is used to specify a smooth term in a `gam()`

model formula.

At the time of writing, `gam`

is not available in R.

lf(..., alpha=0.7, deg=2, scale=1, kern="tcub", ev="tree", maxk=100)

`...` |
numeric predictor variable(s) |

`alpha` |
Smoothing parameter. A single number (e.g. `alpha=0.7` )
is interpreted as a nearest neighbor fraction. With two
componentes (e.g. `alpha=c(0.7,1.2)` ), the first component
is a nearest neighbor fraction, and the second component is
a fixed component. A third component is the penalty term in locally
adaptive smoothing. |

`deg` |
degree of polynomials to be fitted locally. |

`scale` |
A scale to apply to each variable. This is especially important for
multivariate fitting, where variables may be measured in
non-comparable units. It is also used to specify the frequency
for `ang` terms. If `scale=FALSE` (the default) no scaling
is performed. If `scale=TRUE` , marginal standard deviations are used.
Alternatively, a numeric vector can provide scales for the
individual variables. |

`kern` |
Weight function, default = `"tcub"` .
Other choices are `"rect"` , `"trwt"` , `"tria"` ,
`"epan"` , `"bisq"` and `"gauss"` . Choices may be restricted
when derivatives are required; e.g. for confidence bands and some
bandwidth selectors. |

`ev` |
Evaluation Structure, default = `"tree"` . Also available are
`"phull"` , `"data"` , `"grid"` , `"kdtree"` ,
`"kdcenter"` and `"crossval"` . `ev="none"` gives no
evaluation points, effectively producing the global parametric fit.
A vector or matrix of evaluation points can also be provided. |

`maxk` |
Controls space assignment for evaluation structures.
For the adaptive evaluation structures, it is impossible to be sure
in advance how many vertices will be generated. If you get
warnings about `Insufficient vertex space', Locfit's default assigment
can be increased by increasing `maxk` . The default is `maxk=100` . |

`locfit`

,
`locfit.raw`

,
`gam.lf`

,
`gam`

# fit an additive semiparametric model to the ethanol data. if (exists("gam")) { # shut up R's checks fit <- gam(NOx~lf(E)+C,data=ethanol) plot(fit) }

[Package *locfit* version 1.1-9 Index]