Hi Everyone Do you think it is possible to create UDAF to calculate Herfindahl Index (HHI) http://en.wikipedia.org/wiki/Herfindahl_index
Calculation: v ratio ratio^2 100 0.1 0.01 100 0.1 0.01 300 0.3 0.09 100 0.1 0.01 200 0.2 0.04 200 0.2 0.04 ------------------------ SUM 1000 1 0.2 HHI = 0.2 Currently I use the following SQL: select sum(pow(t.v / t2.sum_v, 2)) from t join (select sum(v) sum_v from t) t2 Is it possible to create UDAF for it? e.g. select hhi(v) from t; Lets assume set of v can fit in reducer memory.
