[pgrouting-dev] Fwd: Fwd: an implementation of beta skeletons, relative neighborhood graph and gabriel graphs

[Stephen Woodbridge]

-------- Forwarded Message --------
Subject: 	Fwd: [pgrouting-dev] an implementation of beta skeletons,
relative neighborhood graph and gabriel graphs
Date: 	Tue, 22 Mar 2016 09:21:44 +0000
From: 	dave.potts at pinan.co.uk
To: 	woodbri at swoodbridge.com



Hi Steve,

Sorry to trouble you.

I email this to the development email list and did not get a response.

I know that Beta skelton graphs are not a standard routing style
function but its the sort otf thing I use in my research which is all
about network anaylsis.  I just wondered if anybody else did.

Dave.

-------- Forwarded message -------
From: dave.potts at pinan.co.uk <mailto:dave.potts at pinan.co.uk>
To: pgrouting-dev at lists.osgeo.org <mailto:pgrouting-dev at lists.osgeo.org>
Sent: 19 March 2016 17:28
Subject: [pgrouting-dev] an implementation of beta skeletons, relative
neighborhood graph and gabriel graphs
Is there any interest in any off the above graph forms in the routing
library?

See
https://en.wikipedia.org/wiki/Beta_skeleton
https://en.wikipedia.org/wiki/Relative_neighborhood_graph
https://en.wikipedia.org/wiki/Gabriel_graph

I have implementation with the following method signatures

CREATE OR REPLACE FUNCTION pgr_beta_skelton(sql text, beta float,OUT id
integer ,OUT id1 integer , OUT id2 integer)
    RETURNS SETOF RECORD AS
      '$libdir/librouting-2.1', 'dir_graph_beta_skelton'
      LANGUAGE c STABLE STRICT;

CREATE OR REPLACE FUNCTION pgr_relative_neigborhood_graph(sql text ,OUT
id integer ,OUT id1 integer , OUT id2 integer)
    RETURNS SETOF RECORD AS
      '$libdir/librouting-2.1', 'dir_graph_relative_neigborhood_graph'
      LANGUAGE c STABLE STRICT;

CREATE OR REPLACE FUNCTION pgr_gabriel_graph(sql text ,OUT id integer
,OUT id1 integer , OUT id2 integer)
    RETURNS SETOF RECORD AS
      '$libdir/librouting-2.1', 'dir_graph_gabriel_graph'
      LANGUAGE c STABLE STRICT;

They all take an sql statement of the form

select  st_makeline(v1.the_geom,v2.the_geom) as the_geom  from
   pgr_gabriel_graph('select id,st_x(the_geom) as x ,st_y(the_geom) as y
from tmp_table2'), tmp_table2 v1, tmp_table2 v2 where id1=v1.id and
   id2=v2.id;

Ie the expect an set of objects with an id and a x and y coordinate

In this example tmp_table functions as resource of data, and the above
statement returns a serries of id statements id refers to id of 1st x/y
node and the 2nd id refers to 2md x/y pair
eg
id  | id1 | id2
-----+-----+-----
     1 | 607 | 558
     2 | 606 | 542
     3 | 605 | 594
     4 | 605 | 520
     5 | 604 | 579
     6 | 604 | 525
     7 | 603 | 605
     8 | 603 | 594
     9 | 603 | 530
    10 | 602 | 580
    11 | 602 | 563
    12 | 601 | 537
    13 | 601 | 534
    14 | 600 | 523
    15 | 599 | 601
    16 | 599 | 522
    17 | 598 | 590


regards

Dave.





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