added function overload with subqueries input

doc/07_gravity.md

@@ -1,11 +1,11 @@
 ## Gravity Model
 
-### CDB_Gravity(t_id bigint[], t_geom geometry[], t_weight numeric[], s_id bigint[], s_geom geometry[], s_pop numeric[], target bigint, radius integer, minval numeric DEFAULT -10e307)
-
 Gravity Models are derived from Newton's Law of Gravity and are used to predict the interaction between a group of populated areas (sources) and a specific target among a group of potential targets, in terms of an attraction factor (weight)
 
 **CDB_Gravity** is based on the model defined in *Huff's Law of Shopper attraction (1963)*
 
+### CDB_Gravity(t_id bigint[], t_geom geometry[], t_weight numeric[], s_id bigint[], s_geom geometry[], s_pop numeric[], target bigint, radius integer, minval numeric DEFAULT -10e307)
+
 #### Arguments
 
 | Name | Type | Description |
@@ -20,8 +20,22 @@ Gravity Models are derived from Newton's Law of Gravity and are used to predict
 | radius   | integer     | Radius in meters around the target under study that will be taken into account|
 | minval (optional)   | numeric     | Lowest accepted value of weight, defaults to numeric min_value |
 
+### CDB_Gravity( target_query text, weight_column text, source_query text, pop_column text, target bigint, radius integer, minval numeric DEFAULT -10e307)
+
+#### Arguments
+
+| Name | Type | Description |
+|------|------|-------------|
+| target_query     | text    | Query that defines targets |
+| weight_column   | text  | Column name of weights |
+| source_query     | text    | Query that defines sources |
+| pop_column   | text  | Column name of population |
+| target   | bigint      | cartodb_id of the target under study |
+| radius   | integer     | Radius in meters around the target under study that will be taken into account|
+| minval (optional)   | numeric     | Lowest accepted value of weight, defaults to numeric min_value |
+
 
-#### Returns
+### Returns
 
 | Column Name | Type | Description |
 |-------------|------|-------------|

src/pg/sql/07_gravity.sql

@@ -1,3 +1,34 @@
+CREATE OR REPLACE FUNCTION CDB_Gravity(
+    IN target_query text,
+    IN weight_column text,
+    IN source_query text,
+    IN pop_column text,
+    IN target bigint,
+    IN radius integer,
+    IN minval numeric DEFAULT -10e307
+    )
+RETURNS TABLE(
+    the_geom geometry,
+    source_id bigint,
+    target_id bigint,
+    dist numeric,
+    h numeric,
+    hpop numeric)  AS $$
+DECLARE
+    t_id bigint[];
+    t_geom geometry[];
+    t_weight numeric[];
+    s_id bigint[];
+    s_geom geometry[];
+    s_pop numeric[];
+BEGIN
+    EXECUTE 'WITH foo as('+target_query+') SELECT array_agg(cartodb_id), array_agg(the_geom), array_agg(' || weight_column || ') FROM foo' INTO t_id, t_geom, t_weight;
+    EXECUTE 'WITH foo as('+source_query+') SELECT array_agg(cartodb_id), array_agg(the_geom), array_agg(' || pop_column || ') FROM foo' INTO s_id, s_geom, s_pop;
+    RETURN QUERY
+    SELECT g.* FROM t, s, CDB_Gravity(t_id, t_geom, t_weight, s_id, s_geom, s_pop, target, radius, minval) g;
+END;
+$$ language plpgsql;
+
 CREATE OR REPLACE FUNCTION CDB_Gravity(
     IN t_id bigint[],
     IN t_geom geometry[],