{ "name": "collect", "type": "function", "groups": ["Aggregates"], "description": "Returns the multipart geometry of aggregated geometries from an expression", "arguments": [ {"arg":"expression", "description":"geometry expression to aggregate"}, {"arg":"group_by", "optional":true, "description":"optional expression to use to group aggregate calculations"}, {"arg":"filter", "optional":true, "description":"optional expression to use to filter features used to calculate aggregate"} ], "examples": [ { "expression":"collect( $geometry )", "returns":"multipart geometry of aggregated geometries"}, { "expression":"collect( centroid($geometry), group_by:=\"region\", filter:= \"use\" = 'civilian' )", "returns":"aggregated centroids of the civilian features based on their region value"} ] }