The first graph you can simply set:
For the second graph you can just change the first value of V_PFR to 0 since it has a load of repeated values anyway:
and plot as before.
The final graph suggests that the first 500 values of your V_PFR array should not be constant though. That appears to be more related to the maths than graph scaling. Solving that problem would also mean the second graph should be correct too without the need for the fudge described above.
if X(i) <= 0.5
V_PFR(i) = (-1000/(10^-8/3)*-0.5);
seems to directly contradict what the 3rd graph on that page suggests, giving a constant value for x < 0.5 rather than the decreasing curve shown. That is not something I can help with though as I'm not at all familiar with the equations and can't afford that amount of time to look at them more deeply.