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56 lines
3.0 KiB
Plaintext
56 lines
3.0 KiB
Plaintext
{
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"name": "overlay_nearest",
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"type": "function",
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"groups": ["GeometryGroup"],
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"description": "Returns whether the current feature has feature(s) from a target layer within a given distance, or an array of expression-based results for the features in the target layer within a distance from the current feature.<br><br>Note: This function can be slow and consume a lot of memory for large layers.",
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"arguments": [{
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"arg": "layer",
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"description": "the target layer"
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}, {
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"arg": "expression",
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"description": "an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.",
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"optional": true
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}, {
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"arg": "filter",
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"description": "an optional expression to filter the target features to check. If not set, all the features in the target layer will be used.",
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"optional": true
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}, {
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"arg": "limit",
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"description": "an optional integer to limit the number of matching features. If not set, only the nearest feature will be returned. If set to -1, returns all the matching features.",
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"optional": true,
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"default": "1"
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}, {
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"arg": "max_distance",
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"description": "an optional distance to limit the search of matching features. If not set, all the features in the target layer will be used.",
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"optional": true
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}, {
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"arg": "cache",
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"description": "set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)",
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"optional": true,
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"default": "false"
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}],
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"examples": [{
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"expression": "overlay_nearest('airports')",
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"returns": "TRUE if the \"airports\" layer has at least one feature"
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}, {
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"expression": "overlay_nearest('airports', max_distance:= 5000)",
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"returns": "TRUE if there is an airport within a distance of 5000 map units from the current feature"
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}, {
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"expression": "overlay_nearest('airports', name)",
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"returns": "the name of the closest airport to the current feature, as an array"
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}, {
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"expression": "array_to_string(overlay_nearest('airports', name))",
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"returns": "the name of the closest airport to the current feature, as a string"
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}, {
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"expression": "overlay_nearest(layer:='airports', expression:= name, max_distance:= 5000)",
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"returns": "the name of the closest airport within a distance of 5000 map units from the current feature, as an array"
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}, {
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"expression": "overlay_nearest(layer:='airports', expression:=\"name\", filter:= \"Use\"='Civilian', limit:=3)",
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"returns": "an array of names, for up to the three closest civilian airports ordered by distance"
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}, {
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"expression": "overlay_nearest(layer:='airports', expression:=\"name\", limit:= -1, max_distance:= 5000)",
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"returns": "an array of names, for all the airports within a distance of 5000 map units from the current feature, ordered by distance"
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}],
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"tags": ["distance", "near", "close", "current", "target", "array", "features"]
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}
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