{
  "name": "sum",
  "type": "function",
  "groups": ["Aggregates"],
  "description": "Returns the aggregate summed value from a field or expression.",
  "arguments": [
	{"arg":"expression", "description":"sub expression of field 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":"sum(\"population\",group_by:=\"state\")", "returns":"summed population value, grouped by state field"}
  ]
}