#include Axe3
(Na_2O) (SiO_2) (K_2O) Axe3
/Tbl [
  20.0  25.0
  35.0  15.0
  50.0  16.5
  60.0  5.33
] def
% here I scale to 0..1 instead of 0..100
[ Tbl { 100 div } forall ] Plot