R: Generate a scope for step.Gam

gam.scope {gam} | R Documentation

## Generate a scope for step.Gam

### Description

Given a data.frame as an argument, generate a scope list for use in step.Gam, each element of which gives the candidates for that term.

### Usage

    gam.scope(frame, response=1, smoother = "s", arg = NULL, form = TRUE)

### Arguments

`frame` | a data.frame to be used in `step.Gam`. Apart from the response column, all other columns will be used.
`response` | The column in `frame` used as the response. Default is 1.
`smoother` | which smoother to use for the nonlinear terms; i.e. "s" or "lo", or any other supplied smoother. Default is "s".
`arg` | a character (vector), which is the argument to `smoother`. For example, `arg="df=6"` would result in the expression `s(x,df=6)` for a column named "x". This can be a vector, for example `arg=c("df=4","df=6")`, which would result two smooth terms.
`form` | if `TRUE`, each term is a formula, else a character vector.

### Details

This function creates a similar scope formula for each variable in the frame. A column named "x" by default will generate a scope term `~1+x+s(x)`. With `arg=c("df=4","df=6")` we get `~1+x+s(x,df=4)+s(x,df=6)`. With form=FALSE, we would get the character vector `c("1","x","s(x,df=4)","s(x,df=6")`.

### Value

a scope list is returned, with either a formula or a character vector for each term, which describes the candidates for that term in the Gam.

### Author(s)

Written by Trevor Hastie, following closely the design in the "Generalized Additive Models" chapter (Hastie, 1992) in Chambers and Hastie (1992). This version of `gam.scope` is adapted from the S version.

### References

Hastie, T. J. (1991) Generalized additive models. Chapter 7 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth \& Brooks/Cole.

### See Also

`step.Gam`

### Examples

    data(gam.data)
    gdata=gam.data[,1:3]
    gam.scope(gdata,2)
    gam.scope(gdata,2,arg="df=5")
    gam.scope(gdata,2,arg="df=5",form=FALSE)
    gam.scope(gdata,2,arg=c("df=4","df=6"))

[Package gam version 1.16 Index]