levels.incidence and levels.cover: Levels of a poset
Description
The behaviour of these methods for objects of classes incidence and
cover is different from the behaviour of function
levels for factors. Because of the technical definition it is not possible
to use a different name for these methods.
The methods return a vector associating each profile with the corresponding
level.
Usage
## S3 method for class 'incidence':
levels(x)
## S3 method for class 'cover':
levels(x)