ST_GeometryN takes a geometry column and a numeric column or value (n) and returns a geometry column.
The output column contains the nth single-part geometry from a multipart geometry. When n=0, the first
single-part geometry is returned. If the nth geometry doesn't exist, null is returned.
| Function | Syntax |
|---|---|
| Python | geometry |
| SQL | ST |
| Scala | geometry |
For more details, go to the GeoAnalytics Engine API reference for geometry_n.
This function implements the OpenGIS Simple Features Implementation Specification SQL 1.2.1.
Examples
from geoanalytics.sql import functions as ST, Polygon
data = [
(Polygon([[[40,120],[90,120],[90,150],[40,150],[40,120]],[[50,130],[60,130],[60,140],[50,140],[50,130]]]),),
(Polygon([[[20,0],[30,20],[40,0],[20,0]]]),)
]
df = spark.createDataFrame(data, ["polygon"])
df.select(ST.geometry_n("polygon", 1).alias("geometry_n")).show(truncate=False)Result
+----------------------------------------------------------+
|geometry_n |
+----------------------------------------------------------+
|{"rings":[[[50,130],[60,130],[60,140],[50,140],[50,130]]]}|
|NULL |
+----------------------------------------------------------+Version table
| Release | Notes |
|---|---|
1.0.0 | Python and SQL functions introduced |
1.5.0 | Scala function introduced |