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smart resolution guessing

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This commit is contained in:
abelvm 2016-08-18 16:13:56 -04:00
parent b7a412fa4d
commit 0f47659cf9
3 changed files with 36 additions and 17 deletions
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11
doc/19_contour.md
View File

@ -14,11 +14,11 @@ Function to generate a contour map from an scatter dataset of points, using one
|------|------|-------------|
| geom | geometry[] | Array of points's geometries |
| values | numeric[] | Array of points' values for the param under study|
| resolution | integer | Size in meters of the cells in the grid|
| buffer | numeric | Value between 0 and 1 for spatial buffer of the set of points
| 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 millisecons for processing time
### Returns
Returns a table object
@ -37,11 +37,14 @@ Returns a table object
WITH a AS (
SELECT
ARRAY[800, 700, 600, 500, 400, 300, 200, 100]::numeric[] AS vals,
ARRAY[ST_GeomFromText('POINT(2.1744 41.403)'),ST_GeomFromText('POINT(2.1228 41.380)'),ST_GeomFromText('POINT(2.1511 41.374)'),ST_GeomFromText('POINT(2.1528 41.413)'),ST_GeomFromText('POINT(2.165 41.391)'),ST_GeomFromText('POINT(2.1498 41.371)'),ST_GeomFromText('POINT(2.1533 41.368)'),ST_GeomFromText('POINT(2.131386 41.41399)')] AS g
)
ARRAY[ST_GeomFromText('POINT(2.1744 41.403)',4326),ST_GeomFromText('POINT(2.1228 41.380)',4326),ST_GeomFromText('POINT(2.1511 41.374)',4326),ST_GeomFromText('POINT(2.1528 41.413)',4326),ST_GeomFromText('POINT(2.165 41.391)',4326),ST_GeomFromText('POINT(2.1498 41.371)',4326),ST_GeomFromText('POINT(2.1533 41.368)',4326),ST_GeomFromText('POINT(2.131386 41.41399)',4326)] AS g
),
b as(
SELECT
foo.*
FROM
a,
CDB_contour(a.g, a.vals, 500, 0.0, 1,3,5) 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;
```

40
src/pg/sql/19_contour.sql
View File

@ -1,11 +1,11 @@
CREATE OR REPLACE FUNCTION CDB_Contour(
IN geomin geometry[],
IN colin numeric[],
IN resolution integer,
IN buffer numeric,
IN intmethod integer,
IN classmethod integer,
IN steps integer
IN steps integer,
IN max_time integer DEFAULT 60000
)
RETURNS TABLE(
the_geom geometry,
@ -15,19 +15,28 @@ RETURNS TABLE(
avg_value numeric
) AS $$
DECLARE
cell numeric;
cell_count integer;
tin geometry[];
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;
-- 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;
-- calc the optimal number of cells for the current dataset
SELECT
CASE intmethod
WHEN 0 THEN round(3.7745903782 * max_time - 9.4399210051 * array_length(geomin,1) - 1350.8778213073)
WHEN 1 THEN round(2.2855592156 * max_time - 87.285217133 * array_length(geomin,1) + 17255.7085601797)
WHEN 2 THEN round(0.9799471999 * max_time - 127.0334085369 * array_length(geomin,1) + 22707.9579721218)
ELSE 10000
END INTO cell_count;
-- we don't have iterative barycentric interpolation in CDB_interpolation,
-- and it's a costy function, so let's make a custom one here till
-- we update the code
@ -59,10 +68,17 @@ BEGIN
ST_Transform(e, 3857) as geom
FROM envelope
),
resolution as(
SELECT
round(|/ (
ST_area(geom) / cell_count
)) as cell
FROM envelope3857
),
grid as(
SELECT
ST_Transform(cdb_crankshaft.CDB_RectangleGrid(geom, cell, cell), 4326) as geom
FROM envelope3857
ST_Transform(cdb_crankshaft.CDB_RectangleGrid(e.geom, r.cell, r.cell), 4326) as geom
FROM envelope3857 e, resolution r
),
interp as(
SELECT

2
src/pg/test/sql/19_contour_test.sql
View File

@ -12,6 +12,6 @@ SELECT
foo.*
FROM
a,
cdb_crankshaft.CDB_contour(a.g, a.vals, 500, 0.0, 1, 3, 5) 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;