instances {gnm}

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)

Arguments

term

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

instances

the desired number of instances of the term.

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.

Author(s)

Heather Turner

See Also

gnm, formula, nonlin.function, Mult, MultHomog

Examples

## Not run: 
## (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)

## End(Not run)