I need to sample random numbers from Weibull, Gumbel and Generalized extreme value distributions. Of all of these distributions I know mean and variance. My question is: how can I determine these parameters? Is there any analytical way, or approximation (concerning the approximations, I already found [this one][1] for Weibull, but it is an approximation valid for wind, that is not my case)? Otherwise, how could I do it via an iterative method?


  [1]: http://stats.stackexchange.com/questions/159452/how-can-i-recreate-a-weibull-distribution-given-mean-and-standard-deviation-and