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Add docs for GeoSPARQL function geof:geometryN #8

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20 changes: 19 additions & 1 deletion docs/geosparql.md
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Expand Up @@ -256,7 +256,7 @@ SELECT * WHERE {
```
</details>

`geof:numGeometries(?geom)`<a id="geof-numgeometries"></a>: This function returns the number of child geometries contained in a geometry of a collection type (`MULTIPOINT`, `MULTILINESTRING`, `MULTIPOLYGON` or `GEOMETRYCOLLECTION`) given as `geo:wktLiteral`. It returns an `xsd:integer`. This function benefits from [geometry preprocessing](#geometry-preprocessing).
`geof:numGeometries(?geom)`<a id="geof-numgeometries"></a>: This function returns the number of child geometries contained in a geometry of a collection type (`MULTIPOINT`, `MULTILINESTRING`, `MULTIPOLYGON` or `GEOMETRYCOLLECTION`) given as `geo:wktLiteral`. For single geometries (`POINT`, `LINESTRING`, `POLYGON`) the result is `1`. The result has datatype `xsd:int`. This function benefits from [geometry preprocessing](#geometry-preprocessing).

<details>
<summary>Example query for <code>geof:numGeometries</code></summary><br />
Expand All @@ -276,6 +276,24 @@ LIMIT 100
</details>


`geof:geometryN(?geom, ?n)`<a id="geof-geometryn"></a>: This function returns the n-th child geometry contained in a geometry of a collection type (`MULTIPOINT`, `MULTILINESTRING`, `MULTIPOLYGON` or `GEOMETRYCOLLECTION`) given as `geo:wktLiteral`. The child geometries are indexed starting with `1`. For single geometries (`POINT`, `LINESTRING`, `POLYGON`) the geometry itself is returned at index `1`. For valid geometries and indices the result is a literal with `geo:wktLiteral` datatype, for invalid indices it is `UNDEF`.

<details>
<summary>Example query for <code>geof:geometryN</code></summary><br />

```sparql
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
SELECT * WHERE {
BIND (geof:geometryN("MULTIPOINT(1 2,3 4,5 6,7 8)"^^geo:wktLiteral, 4) AS ?wkt1) # POINT(7 8)
BIND (geof:geometryN("MULTILINESTRING((1 2,3 4),(5 6,7 8,9 0))"^^geo:wktLiteral, 2) AS ?wkt2) # LINESTRING(5 6,7 8,9 0)
BIND (geof:geometryN("POINT(3 4)"^^geo:wktLiteral, 1) AS ?wkt3) # POINT(3 4)
}
```

</details>


## GeoSPARQL Maximum Distance Search

QLever supports each of the following query patterns for a fast maximum distance search:
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