ST_ExteriorRing

ST_ExteriorRing takes a polygon column and returns a linestring column. The linestring represents the exterior ring of the polygon. Multipart polygons will return null.

Function	Syntax
Python	`exterior_ring(polygon)`
SQL	`ST_ExteriorRing(polygon)`

For more details, go to the GeoAnalytics Engine API reference for exterior_ring.

This function implements the OpenGIS Simple Features Implementation Specification for SQL 1.2.1.

Examples

Python

SQL

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from geoanalytics.sql import functions as ST, Polygon

data = [
    (Polygon([[[20,0],[30,20],[40,0],[20,0]]]),),
    (Polygon([[[0,0],[0,10],[10,10],[10,0],[0,0]],[[1,1],[1,2],[2,2],[2,1],[1,1]]]),)
]

df = spark.createDataFrame(data,["polygon"])

df.select(ST.exterior_ring("polygon").alias("exterior_ring")).show(truncate=False)

Result
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+-------------------------------------------------+
|exterior_ring                                    |
+-------------------------------------------------+
|{"paths":[[[20,0],[20,0],[40,0],[30,20],[20,0]]]}|
|NULL                                             |
+-------------------------------------------------+

Version table

Release	Notes
1.0.0	Function introduced

ST_ExteriorRing

Examples

Version table

Related topics