QGIS/resources/function_help/json/roundness

{
  "name": "roundness",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Calculates how close a polygon shape is to a circle. The function Returns TRUE when the polygon shape is a perfect circle and 0 when it is completely flat.",
  "arguments": [{
    "arg": "geometry",
    "description": "a polygon"
  }],
  "examples": [{
    "expression": "round(roundness(geom_from_wkt('POLYGON(( 0 0, 0 1, 1 1, 1 0, 0 0))')), 3)",
    "returns": "0.785"
  }, {
    "expression": "round(roundness(geom_from_wkt('POLYGON(( 0 0, 0 0.1, 1 0.1, 1 0, 0 0))')), 3)",
    "returns": "0.260"
  }],
  "tags": ["polygon", "perfect", "flat", "close", "shape", "calculates", "circle"]
}