sql

lib/sql/scripts-available/CDB_EqualIntervalBins.sql

@@ -0,0 +1,24 @@
+--
+-- Calculate the equal interval bins for a given column
+--
+-- @param in_array An array of numbers to determine the best
+--                   bin boundary
+--
+-- @param breaks The number of bins you want to find.
+--  
+--
+-- Returns: upper edges of bins
+-- 
+--
+
+CREATE OR REPLACE FUNCTION @extschema@.CDB_EqualIntervalBins ( in_array anyarray, breaks INT ) RETURNS anyarray as $$
+WITH stats AS (
+  SELECT min(e), (max(e)-min(e))/breaks AS del
+    FROM (SELECT unnest(in_array) e) AS p)
+SELECT array_agg(bins)
+  FROM (
+    SELECT min + generate_series(1,breaks)*del AS bins
+      FROM stats) q;
+$$ LANGUAGE SQL IMMUTABLE PARALLEL SAFE;
+
+DROP FUNCTION IF EXISTS @extschema@.CDB_EqualIntervalBins( numeric[], integer);