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/*PGR-GNU*****************************************************************
Copyright (c) 2015~2019 Celia Virginia Vergara Castillo
Mail: project@pgrouting.org
------
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
********************************************************************PGR-GNU*/
----------------------
-- pgr_pointsAsPolygon
----------------------
/*
----------------------------------------------------------
-- Draws an alpha shape around given set of points.
-- ** This should be rewritten as an aggregate. **
----------------------------------------------------------
*/
CREATE OR REPLACE FUNCTION pgr_pointsAsPolygon(
VARCHAR, -- query (required)
alpha FLOAT8 DEFAULT 0)
RETURNS geometry AS
$BODY$
DECLARE
geoms geometry[];
vertex_result record;
i BIGINT;
q TEXT;
BEGIN
q = format($$
WITH
a AS (
%1$s
),
b AS (SELECT ST_makePoint(x, y) AS geom FROM a)
SELECT array_agg(geom) FROM b
$$, $1);
-- RAISE NOTICE '%', q;
EXECUTE q INTO geoms;
-- RAISE NOTICE 'length = %', array_length(geoms, 1);
RETURN pgr_alphashape1(geoms, sqrt(alpha), false);
END;
$BODY$
LANGUAGE plpgsql VOLATILE STRICT;
COMMENT ON FUNCTION pgr_pointsAsPolygon(VARCHAR, FLOAT8)
IS 'pgr_pointsAsPolygon
- Parameters:
- An SQL with columns: id, x, y
- Optional Parameters:
- alpha := 0
- Documentation:
- ${PROJECT_DOC_LINK}/pgr_pointsAsPolygon.html
';
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