From 004da32f19e3de12cad8aaf8dfdc21dac70d2c5f Mon Sep 17 00:00:00 2001
From: Andy Eschbacher <andy.eschbacher@gmail.com>
Date: Thu, 22 Sep 2016 14:06:23 -0400
Subject: [PATCH] first add

---
 src/pg/sql/17_weighted_median.sql | 33 +++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 src/pg/sql/17_weighted_median.sql

diff --git a/src/pg/sql/17_weighted_median.sql b/src/pg/sql/17_weighted_median.sql
new file mode 100644
index 0000000..3b3dce8
--- /dev/null
+++ b/src/pg/sql/17_weighted_median.sql
@@ -0,0 +1,33 @@
+CREATE OR REPLACE FUNCTION CDB_WeightedMedianCenter(geoms geometry[], vals numeric[])
+RETURNS geometry(Point, 4326)
+AS $$
+DECLARE
+  i INT;
+  median_val numeric;
+  median_index INT;
+BEGIN
+
+  -- find the median value
+  SELECT percentile_disc(0.5) WITHIN GROUP (ORDER BY v) INTO median_val
+    FROM unnest(vals) As x(v);
+
+  -- find the index of the median value
+  FOR i in 1..array_length(vals, 1)
+  LOOP
+    IF vals[i] < median_val
+    THEN
+      median_index := i;
+      EXIT;
+    END IF;
+  END LOOP;
+
+  -- return the geometry that has the median value of the dataset
+  IF ST_GeometryType(geoms[median_index]) <> 'ST_Point'
+  THEN
+    RETURN ST_Centroid(geoms[median_index]);
+  ELSE
+    RETURN geoms[median_index];
+  END IF;
+
+END;
+$$ LANGUAGE plpgsql;