QGIS/resources/function_help/json/collect

{
  "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"}
  ]
}