gam: gam.scope – R documentation

Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!

gam.scope

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.

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"))

gam

Generalized Additive Models

v1.20

GPL-2

Authors

Trevor Hastie

Initial release

2020-6-27