Hartley Function

The Hartley function is a measure of uncertainty introduced by Ralph Hartley in 1928. If an outcome is picked uniformly at random from a finite set A, the amount of information revealed once the outcome is known is given by the Hartley function, defined as the logarithm, in a chosen base, of the number of elements in A. Because the function depends only on the size of the set from which an outcome is drawn, it quantifies uncertainty purely in terms of the number of equally likely possibilities, with the unit of the resulting measure determined by the base of the logarithm used. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/