Hi and thanks for the response.
I’m not looking for viewportminimum and maximum.
What I try to do is to fix at 600px only the “graphic part”, the representation of my data, without the label of AXIS Y.
With other words I try to have a “pitch=1” for the graphic part (600 points to display = 600 pixel on screen)
I hope I’m clear and sorry for my poor English.