first add

src/pg/sql/18_outliers.sql

@@ -0,0 +1,52 @@
+CREATE OR REPLACE FUNCTION CDB_StaticOutlier(attr numeric, threshold numeric)
+RETURNS numeric
+AS $$
+BEGIN
+
+  RETURN attr > threshold;
+
+END;
+$$ LANGUAGE plpgsql;
+
+
+CREATE OR REPLACE FUNCTION CDB_PercentOutlier(attr numeric[], outlier_fraction numeric, ids int[])
+RETURNS TABLE(outlier boolean, rowid int)
+AS $$
+DECLARE
+  avg_val numeric;
+  out_vals boolean[];
+BEGIN
+
+  SELECT avg(i) INTO avg_val FROM unnest(attr) As x(i);
+
+  SELECT array_agg( i > avg_val * outlier_fraction) INTO out_vals
+  FROM unnest(attr) As x(i);
+
+  RETURN QUERY
+  SELECT unnest(out_vals) As outlier,
+         unnest(ids) As rowid;
+
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION CDB_StdDevOutlier(attrs numeric[], num_deviations numeric, ids int[])
+RETURNS TABLE(outlier boolean, rowid int)
+AS $$
+DECLARE
+  stddev_val numeric;
+  avg_val numeric;
+  out_vals boolean[];
+BEGIN
+
+  SELECT stddev(i), avg(i) INTO stddev_val, avg_val
+  FROM unnest(attrs) As x(i);
+
+  SELECT array_agg(abs(i - avg_val) / stddev_val > num_deviations) INTO out_vals
+  FROM unnest(attrs) As x(i);
+
+
+  RETURN QUERY
+  SELECT unnest(out_vals) As outlier,
+         unnest(ids) As rowid;
+END;
+$$ LANGUAGE plpgsql;