%  用 Matlab 2009a 求解

syms x y

r = sqrt(x*x+y*y)
f_wald = sqrt(3/(2*pi*r^3))*exp( -3*(r-2)^2/(8*r) )
f_eff_1 = f_wald/(2*pi*r)

g = matlabFunction(f_eff_1)

f_eff = @(x) quadgk( @(y) g(x,y) ,-inf,inf)

xx = -2:0.01:2;  %  x坐标
fxx = arrayfun( @(x) f_eff(x) ,xx);  %  f_effective(x)

figure
plot(xx,fxx)