Added basic inequality mesasures: lorenz curve and gini#414

Merged

mmcky merged 3 commits intoQuantEcon:masterfrom cdagnino:inequality_measures

Oct 11, 2018

+153

Commits on Jun 4, 2018

Added basic inequality mesasures: lorenz curve and gini
cdagnino
committed

Commits on Sep 28, 2018

Changed gini from class to function to simplify the use of numba
cdagnino
committed

Commits on Oct 6, 2018

Change docs to reflect changes from object to function
cdagnino
committed