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Update overlay_nearest function help and examples

(cherry picked from commit a494766)
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DelazJ committed Oct 31, 2020
1 parent f491c24 commit 209fb63d4c85b47e30db82fdf5a7ceca782aafe5
Showing with 46 additions and 16 deletions.
  1. +46 −16 resources/function_help/json/overlay_nearest
@@ -2,55 +2,85 @@
"name": "overlay_nearest",
"type": "function",
"groups": ["GeometryGroup"],
"description": "This returns an array of results of an expression evaluated on features from a different layer ordered BY DISTANCE to the current feature, or, if no expression if provided, simply returns whether at least one feature from the other layer was found. Note : this function can be slow and consume a lot of memory for large layers.",
"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 that are within a distance from the current feature.<br><br>Note: This function can be slow and consume a lot of memory for large layers.",
"arguments": [
{
"arg": "layer",
"description": "the other layer"
"description": "the target layer"
},
{
"arg": "expression",
"description": "an optional expression to evaluate on the features from the other layer (if not set, the function will just return a boolean indicating whether there is at least one match)",
"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.",
"optional": true
},
{
"arg": "filter",
"description": "an optional expression to filter the matching features (if not set, all features will be returned)",
"description": "an optional expression to filter the target features to check. If not set, all the features in the target layer will be used.",
"optional": true
},
{
"name": "overlay_nearest",
"type": "function",
"groups": ["GeometryGroup"],
"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.",
"arguments": [
{
"arg": "limit",
"description": "an optional integer to limit the number of matching features (if not set, only the nearest feature will be returned)",
"arg": "layer",
"description": "the target layer"
},
{
"arg": "expression",
"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.",
"optional": true
},
{
"arg": "filter",
"description": "an optional expression to filter the target features to check. If not set, all the features in the target layer will be used.",
"optional": true
},
{
"arg": "limit",
"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.",
"optional": true,
"default": "1"
},
{
"arg": "max_distance",
"description": "an optional maximum distance to limit the number of matching features (if not set, only the nearest feature will be returned)",
"description": "an optional distance to limit the search of matching features. If not set, all the features in the target layer will be used.",
"optional": true
},
{
"arg": "cache",
"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)",
"optional": true,
"default": false
"default": "false"
}
],
"examples": [
{
"expression": "overlay_nearest('regions')",
"returns": "True"
"expression": "overlay_nearest('airports')",
"returns": "true if the \"airports\" layer has at least one feature"
},
{
"expression": "overlay_nearest('airports', max_distance:= 5000)",
"returns": "true if there is an airport within a distance of 5000 map units from the current feature"
},
{
"expression": "overlay_nearest('airports', name)",
"returns": "the name of the closest airport to the current feature"
},
{
"expression": "overlay_nearest('regions', name)",
"returns": "['South Africa', 'Africa', 'World']"
"expression": "overlay_nearest(layer:='airports', expression:= name, max_distance:= 5000)",
"returns": "the name of the closest airport within a distance of 5000 map units from the current feature"
},
{
"expression": "overlay_nearest('regions', name, name != 'World')",
"returns": "['South Africa', 'Africa']"
"expression": "overlay_nearest(layer:='airports', expression:=\"name\", filter:= \"Use\"='Civilian', limit:=3)",
"returns": "an array of names, for up to the three closest civilian airports ordered by distance"
},
{
"expression": "overlay_nearest('regions', name, limit:=1)",
"returns": "['South Africa']"
"expression": "overlay_nearest(layer:='airports', expression:=\"name\", limit:= -1, max_distance:= 5000)",
"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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