Define choice alternatives — choice_alternatives • choicedata

The choice_alternatives object defines the set of choice alternatives.

Usage

choice_alternatives(
  J = 2,
  alternatives = LETTERS[1:J],
  base = NULL,
  ordered = FALSE
)

# S3 method for class 'choice_alternatives'
print(x, ...)

Arguments

J

[integer(1)]
The number \(\geq 2\) of choice alternatives.

alternatives

[character(J)]
Unique labels for the choice alternatives.

base

[character(1)]
The name of the base alternative for alternative-constant covariates, see details.

If NULL (default), it is set to the first element of the sorted alternatives.

ordered

[logical(1)]
Should the supplied order of alternatives be preserved and treated as an intrinsic ranking (for ordered response models)?

When TRUE, the alternatives are kept in the given order.

Otherwise, they are sorted alphabetically.

x

[choice_alternatives]
A choice_alternatives object.

...

Currently not used.

Value

An object of class choice_alternatives, i.e. a character vector of the choice alternatives with attributes:

J: The number of choice alternatives.
base: The name of the base alternative.
ordered: Do the alternatives encode an inherent ordering?

Base alternative

The full set of coefficients for covariates that are constant across alternatives (including alternative-specific constants) is not identified. To achieve identifiability, the coefficient of alternative base is fixed to zero. The other coefficients then have to be interpreted with respect to base. The base alternative is marked with a * when printing a choice_alternatives object.

Examples

choice_alternatives(
  J = 3,
  alternatives = c("gas", "electricity", "oil"),
  base = "gas"
)
#> 
#> ── Choice alternatives 
#> • electricity
#> • gas*
#> • oil