influence.ME (version 0.9-10)

grouping.levels: Returns the levels of a grouping factor in a mixed effects regression model

Description

Helper function returning all the levels of a grouping factor in a mixed effects regression model.

Usage

grouping.levels(model, group)

Value

Returns a character vector containing all the names / labels of levels of the grouping factor.

Arguments

model

Mixed effects model of class 'mer'

group

Grouping factor of 'model' of which the levels are returned

Author

Rense Nieuwenhuis, Ben Pelzer, Manfred te Grotenhuis

Details

Please note that at times different results may be obtained by using nesting.levels(), compared with deriving the levels of the grouping factor directly from the (original) data. This is because nesting.levels() only extracts the nesting levels that were de facto used in the model. Due to missing values, this may diverge from those present in the actual data.

Examples

 if (FALSE) {
 # Penicillin data originates from the lme4 package.
 model <- lmer(diameter ~ (1|plate) + (1|sample), Penicillin)

 grouping.levels(model, "plate")
 grouping.levels(model, "sample")
}