Merge pull request #59 from CartoDB/kmeans

KMeans clustering and weighted centroid analysis

src/pg/sql/11_kmeans.sql

@@ -0,0 +1,51 @@
+CREATE OR REPLACE FUNCTION  CDB_KMeans(query text, no_clusters integer,no_init integer default 20)
+RETURNS table (cartodb_id integer, cluster_no integer) as $$
+    
+    import plpy 
+    plpy.execute('SELECT cdb_crankshaft._cdb_crankshaft_activate_py()')
+    from crankshaft.clustering import kmeans
+    return kmeans(query,no_clusters,no_init)
+
+$$ language plpythonu;
+
+
+CREATE OR REPLACE FUNCTION CDB_WeightedMeanS(state Numeric[],the_geom GEOMETRY(Point, 4326), weight NUMERIC)
+RETURNS Numeric[] AS 
+$$
+DECLARE 
+    newX NUMERIC;
+    newY NUMERIC;
+    newW NUMERIC;
+BEGIN
+    IF weight IS NULL OR the_geom IS NULL THEN 
+        newX = state[1];
+        newY = state[2];
+        newW = state[3];
+    ELSE
+        newX = state[1] + ST_X(the_geom)*weight;
+        newY = state[2] + ST_Y(the_geom)*weight;
+        newW = state[3] + weight;
+    END IF;
+    RETURN Array[newX,newY,newW];
+
+END
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION CDB_WeightedMeanF(state Numeric[])
+RETURNS GEOMETRY AS 
+$$
+BEGIN
+    IF state[3] = 0 THEN 
+        RETURN ST_SetSRID(ST_MakePoint(state[1],state[2]), 4326);
+    ELSE 
+        RETURN ST_SETSRID(ST_MakePoint(state[1]/state[3], state[2]/state[3]),4326);
+    END IF;
+END
+$$ LANGUAGE plpgsql;
+
+CREATE AGGREGATE CDB_WeightedMean(geometry(Point, 4326), NUMERIC)(
+    SFUNC = CDB_WeightedMeanS,
+    FINALFUNC = CDB_WeightedMeanF,
+    STYPE = Numeric[],
+    INITCOND = "{0.0,0.0,0.0}" 
+);