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Nth chain in polygon（多边形中的第N环 (Nth chain in polygon)）

Supported in: Batch, Faster, Streaming

Returns the nth ring in a single polygon in the geometry. Indexing is 1-based, and an index of 0 is out-of-bounds. An index equal to 1 returns an external ring. An index greater than 1 returns an internal ring. Returns null for any of the following conditions: geometry isn't a single polygon, a feature collection or geometry collection is provided, index is out-of-bounds, or at least one argument is null.

Expression categories: Geospatial

Declared arguments

  • N: Index of the ring to retrieve. Indexing is 1-based, and an index of 0 is out-of-bounds. An index greater than 1 returns an internal ring.
    Expression\
  • Polygon: Polygon to retrieve the nth ring of.
    Expression\

Output type: Geometry

Examples

Example 1: Base case

Argument values:

  • N: n
  • Polygon: polygon
polygon n Output
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} 1 {"coordinates": [[0.0, 0.0], [0.0, 10.0], [10.0, 10.0], [10.0, 0.0], [0.0, 0.0]], "type": "LineString"}
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} 2 null
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]]],"type":"Polygon"} 1 {"coordinates": [[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]]],"type":"Polygon"} 2 {"coordinates": [[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]], "type": "LineString"}

Example 2: Null case

Argument values:

  • N: n
  • Polygon: polygon
polygon n Output
{"coordinates": [[[[2.0, 2.0], [7.0, 2.0], [7.0, 7.0], [2.0, 7.0], [2.0, 2.0]]], [[[12.0, 12.0], [17.0, 12.0], [17.0, 17.0], [12.0, 17.0], [12.0, 12.0]]]], "type":"MultiPolygon"} 1 null
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} null null
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} 0 null
null 1 null
null null null

Example 3: Edge case

Argument values:

  • N: n
  • Polygon: polygon
polygon n Output
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 1 {"coordinates": [[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 2 {"coordinates": [[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 3 {"coordinates": [[58.0,58.0],[58.0,59.0],[59.0,59.0],[59.0,58.0],[58.0,58.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 4 {"coordinates": [[52.0,58.5],[56.0,58.5],[54.0,57.5],[52.0,58.5]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 5 null

中文翻译

多边形中的第N环 (Nth chain in polygon)

支持：批处理 (Batch)、快速处理 (Faster)、流处理 (Streaming)

返回几何体中单个多边形的第N个环。索引从1开始，索引0超出范围。索引等于1返回外环，索引大于1返回内环。在以下任一情况下返回null：几何体不是单个多边形、提供了要素集合 (feature collection) 或几何集合 (geometry collection)、索引超出范围、或至少有一个参数为null。

表达式类别： 地理空间 (Geospatial)

声明的参数

  • N： 要检索的环的索引。索引从1开始，索引0超出范围。索引大于1返回内环。
    表达式\
  • Polygon： 要检索第N环的多边形。
    表达式\

输出类型： Geometry

示例

示例1：基本情况

参数值：

  • N： n
  • Polygon： polygon
polygon n 输出
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} 1 {"coordinates": [[0.0, 0.0], [0.0, 10.0], [10.0, 10.0], [10.0, 0.0], [0.0, 0.0]], "type": "LineString"}
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} 2 null
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]]],"type":"Polygon"} 1 {"coordinates": [[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]]],"type":"Polygon"} 2 {"coordinates": [[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]], "type": "LineString"}

示例2：空值情况

参数值：

  • N： n
  • Polygon： polygon
polygon n 输出
{"coordinates": [[[[2.0, 2.0], [7.0, 2.0], [7.0, 7.0], [2.0, 7.0], [2.0, 2.0]]], [[[12.0, 12.0], [17.0, 12.0], [17.0, 17.0], [12.0, 17.0], [12.0, 12.0]]]], "type":"MultiPolygon"} 1 null
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} null null
{"type":"Polygon","coordinates":[[[0.0,0.0],[0.0,10.0],[10.0,10.0],[10.0,0.0],[0.0,0.0]]]} 0 null
null 1 null
null null null

示例3：边界情况

参数值：

  • N： n
  • Polygon： polygon
polygon n 输出
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 1 {"coordinates": [[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 2 {"coordinates": [[57.0,57.0],[55.0,52.0],[52.0,52.0],[50.0,57.0],[57.0,57.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 3 {"coordinates": [[58.0,58.0],[58.0,59.0],[59.0,59.0],[59.0,58.0],[58.0,58.0]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 4 {"coordinates": [[52.0,58.5],[56.0,58.5],[54.0,57.5],[52.0,58.5]], "type": "LineString"}
{"coordinates":[[[60.0,60.0],[50.0,60.0],[50.0,50.0],[60.0,50.0],[60.0,60.0]],[[57.0,57.0],[55.0,52.... 5 null