lowerCalculate lower bounds for a vector of sets with respect to the evidence structure. For more detail see lower
signature(x = "credal", sets = "character")obtain lower bounds for a vector of sets
signature(x = "credal", sets = "missing")obtain lower bounds for all singleton states
signature(x = "mass", sets = "character")obtain the belief, or lower bounds, for a vector of sets
signature(x = "mass", sets = "missing")obtain the belief, or lower bounds, for all singleton states