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, whcih 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.