Changes between Version 4 and Version 5 of DevClusteringFunctions

Timestamp:

02/02/15 12:41:18 (10 years ago)

Author:

mwtoews

Comment:

fix formatting

DevClusteringFunctions

@@ -1 @@
-Proposal for two clustering functions:
+= Proposal for clustering functions =
+
+== `geometry[] ST_ClusterIntersecting(geometry geom)` ==
+
+Aggregate function returning an array of `GeometryCollection`s representing the connected components of a set of geometries.
+
+ - accepts `[Multi]Point`, `[Multi]LineString`, `[Multi]Polygon` geometries of any type that can be converted into GEOS (I can't think of a situation where `[Multi]Point` would be useful, but that doesn't mean there isn't one...)
+ - return a geometry array (my current implementation returns a `GeometryCollection`, but the recursive semantics of `ST_Dump` then undo all of the hard work)
+Example: if run on a table containing all of the `LineString`s in the image below, would return an array with two `MultiLineString` geometries (red and blue)
+
+[[Image(http://i.stack.imgur.com/WNlxX.png)]]
 
 ----
 
-{{{geometry[] ST_ClusterIntersecting(geometry geom)}}}
+== `geometry[] ST_ClusterWithin(geometry geom, double precision distance)` ==
 
-Aggregate function returning an array of GeometryCollections representing the connected components of a set of geometries.
+Aggregate function returning an array of `GeometryCollection`s?/`MultiPoint`s?, where any component is reachable from any other component with jump of no more than the specified distance.
 
-- accepts Point/MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon geometries of any type that can be converted into GEOS (I can't think of a situation where Point/MultiPoint would be useful, but that doesn't mean there isn't one...)[[br]]
-- return a geometry array (my current implementation returns a GeometryCollection, but the recursive semantics of ST_Dump then undo all of the hard work)[[br]]
-Example: if run on a table containing all of the LineStrings in the image below, would return an array with two MultiLineString geometries (red and blue)
+ - like `ST_ClusterIntersecting`, but uses a distance threshold rather than intersection when determining if two geometries should be included in the same component.  Could have an implementation very similar to `ST_ClusterIntersecting`, or could be restricted to points and maybe have a more efficient implementation.
+ - differs from k-means in that a distance is provided, not a number of clusters
 
-[[http://i.stack.imgur.com/WNlxX.png]]
+Example:  In the picture below, an array of five `MultiPoint`s would be returned (color-coded).  The threshold distance in this case was more than the orange line but less than the pink line.
 
-
-----
-
-
-{{{geometry[] ST_ClusterWithin(geometry geom, double precision distance)}}}
-
-Aggregate function returning an array of GeometryCollections?/MultiPoints?, where any component is reachable from any other component with jump of no more than the specified distance.
-
-- like ST_ClusterIntersecting, but uses a distance threshold rather than intersection when determining if two geometries should be included in the same component.  Could have an implementation very similar to ST_ClusterIntersecting, or could be restricted to points and maybe have a more efficient implementation.[[br]]
-- differs from kmeans in that a distance is provided, not a number of clusters[[br]]
-
-Example:  In the picture below, an array of five MultiPoints would be returned (color-coded).  The threshold distance in this case was more than the orange line but less than the pink line.
-
-[[http://ibin.co/1oH1ApWCoW8L]]
+[[Image(http://ibin.co/1oH1ApWCoW8L)]]