s=1.34*10^-5;
mo=1.34*10^-5;
z=16.87*10^-4;
x=2.51*10^7;
k=103;
r=linspace(0,2,50);
F=(s./r.^2)*mo*exp(z).*(exp(-x*r.^2)).*(exp(-x*r.^2)).*(4*k*r.*(cosh(4*k*r))-sinh(4*k*r));
plot(r,F)
Above code most values are zero, please check the typical values of the parameters again or expression?
Are you looking for fplot (function plot) with function handle, see detail
HTH
