first add

.travis.yml

@@ -38,12 +38,11 @@ before_install:
   - sudo apt-get -y remove --purge postgis
   - sudo apt-get -y autoremove
 
-  # - sudo apt-get -y install libgdal1h=1.11.0-0cdb1~precise3
   - sudo apt-get -y install postgresql-9.5=9.5.2-2ubuntu1
   - sudo apt-get -y install postgresql-server-dev-9.5=9.5.2-2ubuntu1
   - sudo apt-get -y install postgresql-plpython-9.5=9.5.2-2ubuntu1
-  - sudo apt-get -y install postgresql-9.5-postgis-scripts=2.2.2.0-cdb2
   - sudo apt-get -y install postgresql-9.5-postgis-2.2=2.2.2.0-cdb2
+  - sudo apt-get -y install postgresql-9.5-postgis-scripts=2.2.2.0-cdb2
 
   # configure it to accept local connections from postgres
   - echo -e "# TYPE  DATABASE        USER            ADDRESS                 METHOD \nlocal   all             postgres                                trust\nlocal   all             all                                     trust\nhost    all             all             127.0.0.1/32            trust" \

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;