%--------------------------------------
%  Log normal distribution
%  Forgot the sqrt(2) in the first version
%--------------------------

x_dB = [6: -0.1 : -40];
s_dB = [4: 2: 12];
temp = x_dB';

for i = 1:length(s_dB)
    nx = x_dB/s_dB(i);
    ii = find(x_dB < 0);
    
    pdf1 = 0.5 - 0.5*erf(-nx(ii)/sqrt(2));
    ii = find(x_dB >= 0);
    pdf2 = 0.5 + 0.5*erf(nx(ii)/sqrt(2));
    
    semilogy(x_dB, [pdf2 pdf1]);
    hold on
    temp = [temp [pdf2 pdf1]']
end

grid
hold off