thank you for your answer but I need a phase plane, not F(r) as m(r) diagram...some things like the https://fr.maplesoft.com/applications/view.aspx?SID=4853&view=html

@Christian Wolinski

dear C. Wolinski your code is broken in thrid line in maple 18 and I got the error. please set coordinate and guide me.

with best regard

@Preben Alsholm 

Thank you a lot

But I have another question: if I want to plot diff(a(t),t)/a(t) or a(t)^-1, what am I doing now?

regards

@Markiyan Hirnyk 

if you see third page of cited article you see likelihood is mentioned  below section 3 my friend .... moreover to calculate likelihood only after find X we need to calculate exp(-X/2)