Changes between Version 1 and Version 2 of UsersWikiCardinalDirection

Timestamp:

04/06/15 19:22:00 (10 years ago)

Author:

mwtoews

Comment:

update style and example

UsersWikiCardinalDirection

@@ -4 +4 @@
 
 {{{
--- Function: ST_Cardinal_Direction(azimuth float8)
--- Returns N, NW, W, SW, S, SE, E, or NE from an azimuth direction
--- By: Mike Toews
---
--- Usage:
--- postgis=# SELECT ST_Cardinal_Direction(
--- postgis(#          ST_Azimuth('POINT(3 5)', 'POINT(5 5)'));
---  st_cardinal_direction
--- -----------------------
---  E
--- (1 row)
---
--- DROP FUNCTION ST_Cardinal_Direction(float8);
+CREATE OR REPLACE FUNCTION ST_CardinalDirection(azimuth float8) RETURNS character varying AS
+$BODY$SELECT CASE
+  WHEN $1 < 0.0 THEN 'less than 0'
+  WHEN degrees($1) < 22.5 THEN 'N'
+  WHEN degrees($1) < 67.5 THEN 'NE'
+  WHEN degrees($1) < 112.5 THEN 'E'
+  WHEN degrees($1) < 157.5 THEN 'SE'
+  WHEN degrees($1) < 202.5 THEN 'S'
+  WHEN degrees($1) < 247.5 THEN 'SW'
+  WHEN degrees($1) < 292.5 THEN 'W'
+  WHEN degrees($1) < 337.5 THEN 'NW'
+  WHEN degrees($1) <= 360.0 THEN 'N'
+END;$BODY$ LANGUAGE sql IMMUTABLE COST 100;
+COMMENT ON FUNCTION ST_CardinalDirection(float8) IS 'input azimuth in radians; returns N, NW, W, SW, S, SE, E, or NE';
+}}}
 
-CREATE OR REPLACE FUNCTION ST_Cardinal_Direction(azimuth float8)
-  RETURNS character varying AS
-$BODY$SELECT CASE
-WHEN $1 < 0.0 THEN 'less than 0'
-WHEN $1*180/pi() < 22.5 THEN 'N'
-WHEN $1*180/pi() < 67.5 THEN 'NE'
-WHEN $1*180/pi() < 112.5 THEN 'E'
-WHEN $1*180/pi() < 157.5 THEN 'SE'
-WHEN $1*180/pi() < 202.5 THEN 'S'
-WHEN $1*180/pi() < 247.5 THEN 'SW'
-WHEN $1*180/pi() < 292.5 THEN 'W'
-WHEN $1*180/pi() < 337.5 THEN 'NW'
-WHEN $1*180/pi() <= 360.0 THEN 'N'
-END;$BODY$ LANGUAGE sql IMMUTABLE COST 100;
-COMMENT ON FUNCTION ST_Cardinal_Direction(float8) IS 'input azimuth in radians; returns N, NW, W, SW, S, SE, E, or NE';
+Example:
+{{{
+SELECT
+  degrees(ST_Azimuth(origin, pt)) AS azimuth_in_degrees,
+  ST_CardinalDirection(ST_Azimuth(origin, pt))
+FROM (
+  SELECT
+    'POINT(0 0)'::geometry AS origin,
+    ST_MakePoint(cos(radians(x)), sin(radians(x))) AS pt
+  FROM generate_series(0, 365, 15) AS x
+) AS f;
+
+  azimuth_in_degrees   | st_cardinaldirection
+-----------------------+----------------------
+                    90 | E
+                    75 | E
+                    60 | NE
+                    45 | NE
+                    30 | NE
+                    15 | N
+ 3.50835464926744e-015 | N
+                   345 | N
+                   330 | NW
+                   315 | NW
+                   300 | NW
+                   285 | W
+                   270 | W
+                   255 | W
+                   240 | SW
+                   225 | SW
+                   210 | SW
+                   195 | S
+                   180 | S
+                   165 | S
+                   150 | SE
+                   135 | SE
+                   120 | SE
+                   105 | E
+                    90 | E
+(25 rows)
 }}}