Two scales defined by a function

Thank you in advance!

Minor correction to exactly reproduce my figure:
I forgot to update my example code in the original post (it uses wmin = 1, wmax = 4.12) and I cannot edit it now unfortunately. So as I said in the text I manually set wmin = 3, wmax = 9, that translates to code like this:

// draw manual axis with manual limits with an offset then color it blue
TGaxis *axis2 = new TGaxis(gPad->GetUxmin(), gPad->GetUymax()-20,
                               gPad->GetUxmax(), gPad->GetUymax()-20, 3, 9, 510, "+L");

I would also appreciate if you could mention to him my other topic TRatioPlot confidence bands - limiting, asymmetry, which I have not received a reply to for some time.

If you need further clarification about my problems, feel free to ask!

Cheers,
Lex