Changes between Initial Version and Version 1 of UsersWikiComputeMultiCentroid

Timestamp:

04/14/09 11:03:07 (16 years ago)

Author:

pierre

Comment:

--

UsersWikiComputeMultiCentroid

@@ +1 @@
+= Compute Multi Centroid =
+
+
+
+{{{
+ -- Function: st_multicentroid(geometry)
+ -- Returns a MULTIPOINT obtained from collecting all
+ -- centroids in the supplied MULTI* geometry.
+ --   by: Mike Toews
+ --
+ -- Usage:
+ -- postgis=# select [ST_AsText|http://postgis.refractions.net/documentation/manual-svn/ST_AsText.html](ST_!MultiCentroid(
+ -- postgis(#       'MULTIPOLYGON (
+ -- postgis'#         (( 0 0, 0 1, 1 1, 1 0, 0 0 )),
+ -- postgis'#         (( 2 2, 2 3, 3 3, 3 2, 2 2 ))
+ -- postgis'#        )'::geometry));
+ --           st_astext
+ -- -----------------------------
+ --  MULTIPOINT(0.5 0.5,2.5 2.5)
+ --( 1 row)
+ --
+ -- DROP FUNCTION ST_!MultiCentroid(geometry);
+
+ CREATE OR REPLACE FUNCTION ST_!MultiCentroid(geometry)
+   RETURNS geometry AS
+ $BODY$SELECT [ST_Collect|http://postgis.refractions.net/documentation/manual-svn/ST_Collect.html](the_geom)
+ FROM (
+  SELECT [ST_Centroid|http://postgis.refractions.net/documentation/manual-svn/ST_Centroid.html](([ST_Dump|http://postgis.refractions.net/documentation/manual-svn/ST_Dump.html]([ST_Multi|http://postgis.refractions.net/documentation/manual-svn/ST_Multi.html]($1))).geom) AS the_geom
+ ) AS foo;$BODY$
+   LANGUAGE 'sql' IMMUTABLE
+   COST 100;
+
+}}}