scheme= getParam( 'scheme', 'scatter', 'data scheme (type)', ['scatter','series'] )

n= getParam( 'n', 1000000, 'number of points' )
seed= getParam( 'seed', 5334, 'random seed (0=no seed)' )
modu= getParam( 'mod', 'F', 'mod of data to limit extent', ['T','F'] )