function [mu, sigma]=lognorparams(mean,stddev)

% From the mean and standard deviation of the lognormal distribution,
% this function computes the parameters mu and sigma of the density
% phi((log t - mu)/sigma)/(sigma*t)

b=1+(stddev/mean)^2;
a=mean/sqrt(b);

mu=log(a);
sigma=sqrt(log(b));