{
  "name": "roundness",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Calculates how close a polygon shape is to a circle. The function returns 1 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"}
  ]
}