gnm (version 1.1-5)

instances: Specify Multiple Instances of a Nonlinear Term in a gnm Model Formula

Description

A symbolic wrapper, for use in the formula argument to gnm, to specify multiple instances of a term specified by a function with an inst argument.

Usage

instances(term, instances = 1)

Value

A deparsed expression representing the summation of term

specified with inst = 1, inst = 2, ..., inst = instances, which is used to create an expanded formula.

Arguments

term

a call to a function with an inst argument, which specifies some term.

instances

the desired number of instances of the term.

Author

Heather Turner

See Also

gnm, formula, nonlin.function, Mult, MultHomog

Examples

if (FALSE) {
## (this example can take quite a while to run)
##
## Fitting two instances of a multiplicative interaction (i.e. a
## two-component interaction)
yield.scaled <- wheat$yield * sqrt(3/1000)
treatment <- factor(paste(wheat$tillage, wheat$summerCrop, wheat$manure,
                          wheat$N, sep = ""))
bilinear2 <- gnm(yield.scaled ~ year + treatment +
                 instances(Mult(year, treatment), 2),
                 family = gaussian, data = wheat)
}