Hartley function

Introduced by Ralph Hartley in 1928.

the Hartley function

1. (mathematics) A measure of uncertainty. If a sample from a finite set A uniformly at random is picked, the information revealed after the outcome is known is given by the Hartley function ${\displaystyle H_{0}(A):=\mathrm {log} _{b}\vert A\vert }$, where ${\displaystyle \vert A\vert }$ denotes the cardinality of A.