Nth point in linestring（线串中的第N个点（Nth point in linestring））¶
Supported in: Batch, Faster, Streaming
Returns the nth point in a single linestring in the geometry. Indexing is 1-based, and an index of 0 is out-of-bounds. A negative index is counted backwards from the end of the linestring, so that -1 is the last point. Returns null for any of the following conditions: geometry isn't a single linestring, 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¶
- Linestring: Linestring to retrieve the nth point of.
Expression\ - N: Index of the point to retrieve. Indexing is 1-based, and an index of 0 is out-of-bounds. A negative index is counted backwards from the end of the linestring, so that -1 is the last point.
Expression\
Output type: GeoPoint
Examples¶
Example 1: Base case¶
Argument values:
- Linestring:
linestring - N:
n
| linestring | n | Output |
|---|---|---|
| {"type":"LineString","coordinates":[[30.0,2.0],[35.0,0.0],[50.0,3.0]]} | 1 | { latitude: 2.0, longitude: 30.0, } |
| {"type":"LineString","coordinates":[[30.0,2.0],[35.0,0.0],[50.0,3.0]]} | 3 | { latitude: 3.0, longitude: 50.0, } |
| {"type":"LineString","coordinates":[[45.0,9.0],[90.0,4.0],[40.0,0.0]]} | -1 | { latitude: 0.0, longitude: 40.0, } |
Example 2: Null case¶
Argument values:
- Linestring:
linestring - N:
n
| linestring | n | Output |
|---|---|---|
| {"type":"LineString","coordinates":[[10.0,4.0],[75.0,0.0]]} | null | null |
| null | 1 | null |
Example 3: Edge case¶
Argument values:
- Linestring:
linestring - N:
n
| linestring | n | Output |
|---|---|---|
| {"type":"MultiLineString","coordinates":[[[100.0,0.0]], [[102.0,2.0]]]} | 2 | null |
| {"type":"GeometryCollection","geometries":{"type":"LineString","coordinates":[[10.0,4.0]]}} | 1 | null |
| {"type":"LineString","coordinates":[[10.0,4.0],[75.0,0.0],[25.0,3.0]]} | 0 | null |
| {"type":"LineString","coordinates":[[12.0,3.0],[76.0,2.0],[98.0,8.0]]} | 4 | null |
| {"type":"LineString","coordinates":[[90.0,1.0],[34.0,1.0],[19.0,7.0]]} | -4 | null |
中文翻译¶
线串中的第N个点（Nth point in linestring）¶
支持：批处理（Batch）、快速处理（Faster）、流处理（Streaming）
返回几何图形中单个线串的第N个点。索引从1开始，索引0表示越界。负索引从线串末尾向前计数，因此-1表示最后一个点。在以下任一情况下返回null：几何图形不是单个线串、提供了要素集合（feature collection）或几何集合（geometry collection）、索引越界，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¶
- Linestring（线串）： 要从中获取第N个点的线串。
表达式\ - N： 要获取的点的索引。索引从1开始，索引0表示越界。负索引从线串末尾向前计数，因此-1表示最后一个点。
表达式\
输出类型： GeoPoint
示例¶
示例1：基本情况¶
参数值：
- Linestring：
linestring - N：
n
| linestring | n | 输出 |
|---|---|---|
| {"type":"LineString","coordinates":[[30.0,2.0],[35.0,0.0],[50.0,3.0]]} | 1 | { latitude（纬度）：2.0, longitude（经度）：30.0, } |
| {"type":"LineString","coordinates":[[30.0,2.0],[35.0,0.0],[50.0,3.0]]} | 3 | { latitude（纬度）：3.0, longitude（经度）：50.0, } |
| {"type":"LineString","coordinates":[[45.0,9.0],[90.0,4.0],[40.0,0.0]]} | -1 | { latitude（纬度）：0.0, longitude（经度）：40.0, } |
示例2：空值情况¶
参数值：
- Linestring：
linestring - N：
n
| linestring | n | 输出 |
|---|---|---|
| {"type":"LineString","coordinates":[[10.0,4.0],[75.0,0.0]]} | null | null |
| null | 1 | null |
示例3：边界情况¶
参数值：
- Linestring：
linestring - N：
n
| linestring | n | 输出 |
|---|---|---|
| {"type":"MultiLineString","coordinates":[[[100.0,0.0]], [[102.0,2.0]]]} | 2 | null |
| {"type":"GeometryCollection","geometries":{"type":"LineString","coordinates":[[10.0,4.0]]}} | 1 | null |
| {"type":"LineString","coordinates":[[10.0,4.0],[75.0,0.0],[25.0,3.0]]} | 0 | null |
| {"type":"LineString","coordinates":[[12.0,3.0],[76.0,2.0],[98.0,8.0]]} | 4 | null |
| {"type":"LineString","coordinates":[[90.0,1.0],[34.0,1.0],[19.0,7.0]]} | -4 | null |