Merge pull request #120 from CartoDB/add-contour

Let the user set the resolution [19]

doc/19_contour.md

@@ -18,7 +18,7 @@ Function to generate a contour map from an scatter dataset of points, using one
 | method   | integer     | 0:nearest neighbor, 1: barycentric, 2: IDW|
 | classmethod   | integer     | 0:equals, 1: heads&tails, 2:jenks, 3:quantiles |
 | steps   | integer     | Number of steps in the classification|
-| max_time   | integer     | Max time in milliseconds for processing time
+| max_time   | integer     | if <= 0: max processing time in seconds (smart resolution) , if >0: resolution in meters
 
 ### Returns
 Returns a table object

src/pg/sql/19_contour.sql

@@ -17,16 +17,15 @@ RETURNS TABLE(
 DECLARE
     cell_count integer;
     tin geometry[];
+    resolution integer;
 BEGIN
-    -- calc the cell size in web mercator units
-    -- WITH center as (
-    --     SELECT ST_centroid(ST_Collect(geomin)) as c
-    -- )
-    -- SELECT
-    --     round(resolution / cos(ST_y(c) * pi()/180))
-    --     INTO cell
-    -- FROM center;
-    -- raise notice 'Resol: %', cell;
+
+    -- nasty trick to override issue #121
+    IF max_time = 0 THEN
+        max_time = -90;
+    END IF;
+    resolution := max_time;
+    max_time := -1 * resolution;
 
     -- calc the optimal number of cells for the current dataset
     SELECT
@@ -70,9 +69,13 @@ BEGIN
     ),
     resolution as(
         SELECT
-             round(|/ (
-                 ST_area(geom) / cell_count
-             )) as cell
+            CASE WHEN resolution <= 0  THEN
+                round(|/ (
+                 ST_area(geom) / abs(cell_count)
+             ))
+            ELSE
+                resolution
+            END AS cell
         FROM envelope3857
     ),
     grid as(

src/pg/test/sql/19_contour_test.sql

@@ -12,6 +12,6 @@ SELECT
     foo.*
 FROM
     a,
-    cdb_crankshaft.CDB_contour(a.g, a.vals,  0.0, 1, 3, 5, 60) foo
+    cdb_crankshaft.CDB_contour(a.g, a.vals,  0.0, 1, 3, 5, -60) foo
 )
 SELECT bin, avg_value from b order by bin;