131 lines
3.9 KiB
PL/PgSQL
131 lines
3.9 KiB
PL/PgSQL
-- 0: nearest neighbor
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-- 1: barymetric
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-- 2: IDW
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CREATE OR REPLACE FUNCTION CDB_SpatialInterpolation(
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IN query text,
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IN point geometry,
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IN method integer DEFAULT 1,
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IN p1 numeric DEFAULT 0,
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IN p2 numeric DEFAULT 0
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)
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RETURNS numeric AS
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$$
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DECLARE
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gs geometry[];
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vs numeric[];
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output numeric;
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BEGIN
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EXECUTE 'WITH a AS('||query||') SELECT array_agg(the_geom), array_agg(attrib) FROM a' INTO gs, vs;
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SELECT CDB_SpatialInterpolation(gs, vs, point, method, p1,p2) INTO output FROM a;
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RETURN output;
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END;
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$$
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language plpgsql IMMUTABLE;
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CREATE OR REPLACE FUNCTION CDB_SpatialInterpolation(
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IN geomin geometry[],
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IN colin numeric[],
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IN point geometry,
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IN method integer DEFAULT 1,
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IN p1 numeric DEFAULT 0,
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IN p2 numeric DEFAULT 0
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)
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RETURNS numeric AS
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$$
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DECLARE
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gs geometry[];
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vs numeric[];
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gs2 geometry[];
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vs2 numeric[];
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g geometry;
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vertex geometry[];
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sg numeric;
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sa numeric;
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sb numeric;
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sc numeric;
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va numeric;
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vb numeric;
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vc numeric;
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output numeric;
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BEGIN
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output := -999.999;
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-- nearest
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IF method = 0 THEN
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WITH a as (SELECT unnest(geomin) as g, unnest(colin) as v)
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SELECT a.v INTO output FROM a ORDER BY point<->a.g LIMIT 1;
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RETURN output;
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-- barymetric
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ELSIF method = 1 THEN
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WITH a as (SELECT unnest(geomin) AS e),
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b as (SELECT ST_DelaunayTriangles(ST_Collect(a.e),0.001, 0) AS t FROM a),
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c as (SELECT (ST_Dump(t)).geom as v FROM b),
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d as (SELECT v FROM c WHERE ST_Within(point, v))
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SELECT v INTO g FROM d;
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IF g is null THEN
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-- out of the realm of the input data
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RETURN -888.888;
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END IF;
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-- vertex of the selected cell
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WITH a AS (SELECT (ST_DumpPoints(g)).geom AS v)
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SELECT array_agg(v) INTO vertex FROM a;
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-- retrieve the value of each vertex
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WITH a AS(SELECT unnest(geomin) as geo, unnest(colin) as c)
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SELECT c INTO va FROM a WHERE ST_Equals(geo, vertex[1]);
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WITH a AS(SELECT unnest(geomin) as geo, unnest(colin) as c)
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SELECT c INTO vb FROM a WHERE ST_Equals(geo, vertex[2]);
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WITH a AS(SELECT unnest(geomin) as geo, unnest(colin) as c)
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SELECT c INTO vc FROM a WHERE ST_Equals(geo, vertex[3]);
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SELECT ST_area(g), ST_area(ST_MakePolygon(ST_MakeLine(ARRAY[point, vertex[2], vertex[3], point]))), ST_area(ST_MakePolygon(ST_MakeLine(ARRAY[point, vertex[1], vertex[3], point]))), ST_area(ST_MakePolygon(ST_MakeLine(ARRAY[point,vertex[1],vertex[2], point]))) INTO sg, sa, sb, sc;
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output := (coalesce(sa,0) * coalesce(va,0) + coalesce(sb,0) * coalesce(vb,0) + coalesce(sc,0) * coalesce(vc,0)) / coalesce(sg);
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RETURN output;
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-- IDW
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-- p1: limit the number of neighbors, 0->no limit
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-- p2: order of distance decay, 0-> order 1
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ELSIF method = 2 THEN
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IF p2 = 0 THEN
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p2 := 1;
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END IF;
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WITH a as (SELECT unnest(geomin) as g, unnest(colin) as v),
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b as (SELECT a.g, a.v FROM a ORDER BY point<->a.g)
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SELECT array_agg(b.g), array_agg(b.v) INTO gs, vs FROM b;
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IF p1::integer>0 THEN
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gs2:=gs;
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vs2:=vs;
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FOR i IN 1..p1
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LOOP
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gs2 := gs2 || gs[i];
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vs2 := vs2 || vs[i];
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END LOOP;
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ELSE
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gs2:=gs;
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vs2:=vs;
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END IF;
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WITH a as (SELECT unnest(gs2) as g, unnest(vs2) as v),
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b as (
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SELECT
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(1/ST_distance(point, a.g)^p2::integer) as k,
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(a.v/ST_distance(point, a.g)^p2::integer) as f
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FROM a
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)
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SELECT sum(b.f)/sum(b.k) INTO output FROM b;
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RETURN output;
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END IF;
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RETURN -777.777;
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END;
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$$
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language plpgsql IMMUTABLE;
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