// GroupBy + Mean
uses DataFrameABC;

begin
  var df := DataFrame.FromCsvText('''
  name,age,score
  Alice,20,85
  Bob,22,90
  Charlie,21,78
  Bob,22,90
  Clara,,78
  Kat,21,NA
  ''');
  
  df.GroupBy('age').Mean('score').Print;
end.