@mmcdara 

Hi Thanks for the reply. The p is a function itself caculated by fsolve, i.e. f(x,y)=x-y+p(x,y) where there is a fsolve in p(x,y).

@Preben Alsholm 

@Carl Love 

Thanks for your helpful reply. The first question is solved.

Could you please explain more how to plot the ProbabilityFunction for R1, and R1+R2?

i am thinking something like: plot(ProbabilityFunction(R1,x))