Package to calculate statistical index numbers.
An index number is "(a) statistic which assigns a single number to several individual statistics in order to quantify trends." (From MathWorld's "Index Number").
This package allows the calculation of some of the better known index numbers: Bowley index, Fisher index, Geometric mean index, Harmonic mean index, Laspeyres' index, Marshall-Edgeworth index, Mitchell index, Paasche's index, and Walsh index.
This was old code I wrote circa 2005, modifying it to use some of the PHP 7 new capabilities
-- Jesus M. Castagnetto