ST_PointN takes a geometry column and an integer and returns a point column. The output column represents
the nth point in the input geometry, where 0 is the first point. If the nth point does not exist
the function returns null. This function always returns null for multipart linestrings and multipart polygons.
| Function | Syntax |
|---|---|
| Python | point |
| SQL | ST |
| Scala | point |
For more details, go to the GeoAnalytics Engine API reference for point_n.
This function implements the OpenGIS Simple Features Implementation Specification for SQL 1.2.1.
Examples
from geoanalytics.sql import functions as ST
data = [
("POINT (10 30)",),
("MULTIPOINT (0 0, 5 5, 0 5)", ),
("LINESTRING (15 15, 10 15, 12 2)", ),
("POLYGON ((20 30, 18 28, 22 35, 40 20))", ),
("MULTILINESTRING ((0 0, 10 10), (10 10, 20 20))", )
]
df = spark.createDataFrame(data, ["wkt"])\
.select(ST.geom_from_text("wkt").alias("geometry"))
df.select(ST.point_n("geometry", 2).alias("point_n")).show()Result
+---------------+
| point_n|
+---------------+
| NULL|
| {"x":0,"y":5}|
| {"x":12,"y":2}|
|{"x":22,"y":35}|
| NULL|
+---------------+Version table
| Release | Notes |
|---|---|
1.0.0 | Python and SQL functions introduced |
1.5.0 | Scala function introduced |