Calculate the Disease Severity Index (DSI) (class for each unit)
DSI.Rd
This function calculates the Disease Severity Index (DSI) based on the provided unit, class, and maximum class value. The DSI is computed by aggregating the classes, calculating weights by multiplying the frequency of each class by the class itself, and then dividing the sum of these weights by the product of the total number of entries and the maximum class value, then multiplying by 100.