uscale function

Utility Scale of an EBA Choice Model

Extract the (normalized) utility scale for an elimination-by-aspects (EBA) model.

uscale(object, norm = "sum", log = FALSE)

Arguments

• object: an object of class eba, typically the result of a call to eba
• norm: either sum, so the scale values sum to unity (default); or a number from 1 to number of stimuli, so this scale value becomes one; or NULL (no normalization)
• log: should the log of the utility scale values be returned? Defaults to FALSE.

Details

Each utility scale value is defined as the sum of aspect values (EBA model parameters) that characterize a given stimulus. First these sums are computed for all stimuli, then normalization (if any) is applied. As each type of normalization corresponds to a multiplication by a positive real number, the ratio between scale values remains constant.

Returns

The (normalized) utility scale of the stimuli.

See Also

eba, cov.u, wald.test.

Examples

data(drugrisk)
A <- list(c(1), c(2,7), c(3,7), c(4,7,8), c(5,7,8), c(6,7,8))
eba1 <- eba(drugrisk[, , group = "male30"], A)  # EBA model

uscale(eba1)                    # sum-to-unity normalization
uscale(eba1, norm=1)            # u(alcohol) := 1
uscale(eba1, norm=5)            # u(heroine) := 1
uscale(eba1, norm=NULL)         # no normalization
uscale(eba1, norm=1, log=TRUE)  # log utility scale, log u(alcohol) := 0