Generate a scope for step.Gam

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.

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.

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").

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.

Author

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.

Examples


data(gam.data)
gdata=gam.data[,1:3]
gam.scope(gdata,2)
#> $x
#> ~1 + x + s(x)
#> <environment: 0x590fc81c1e70>
#> 
#> $z
#> ~1 + z + s(z)
#> <environment: 0x590fc81c1e70>
#> 
gam.scope(gdata,2,arg="df=5")
#> $x
#> ~1 + x + s(x, df = 5)
#> <environment: 0x590fc8229620>
#> 
#> $z
#> ~1 + z + s(z, df = 5)
#> <environment: 0x590fc8229620>
#> 
gam.scope(gdata,2,arg="df=5",form=FALSE)
#> $x
#> [1] "1"         "x"         "s(x,df=5)"
#> 
#> $z
#> [1] "1"         "z"         "s(z,df=5)"
#> 
gam.scope(gdata,2,arg=c("df=4","df=6"))
#> $x
#> ~1 + x + s(x, df = 4) + s(x, df = 6)
#> <environment: 0x590fc83214e8>
#> 
#> $z
#> ~1 + z + s(z, df = 4) + s(z, df = 6)
#> <environment: 0x590fc83214e8>
#>