Regarding fitting a Weibull two parameters probability density function (pdf), with the
fitdistr from MASS package, in R:
1 - What is the iteration algorithm/method used for scale and shape Maximum Likelihood Estimation (MLE)?
There are Nelder–Mead, quasi-Newton and conjugate-gradient algorithms, but I am not sure which one is used for the iteration process on Weibull 2 parameters pdf MLE.
2 - Based on the answer to question 1, what would be a good reference to study the method?