You must define all your variables and a time array with a time step " dt ". Then you write R a variable using all constants defined and the time array. Finally, R and the time array should have the same size, so you could plot them using plot(time_array,R)...
for example :
dx = 0.1;
x = 0:dx:10;
cst = 5;
y = cos(x) + cst;
plot(x,y);
