virgil/commit

FIX chi calculation

diff --git a/api/reports.pl b/api/reports.pl
index 505677e..55aa6db 100644
--- a/api/reports.pl
+++ b/api/reports.pl
@@ -215,7 +215,7 @@ http_chi(Request) :-
 	),
 	contingency_table(Drug, DrugMatch, Reaction,
 			  A,B,C,D,AB,AC,BD,CD,ABCD),
-	Chi is (A/C)/(AB/ABCD),
+	Chi is ((A*D-B*C)^2*(A+B+C+D))/(AB*CD*BD*AC),
 	reply_json(json([chi=Chi,
 			 formula='(ad-bc)^2(a+b+c+d)/((a+b)*(c+d)*(b+d)*(a+c))',
 			 a=A,