I love Optimisation part of software and use this very simple model to find best set of parameters to fit probability curve to observed runoff series, i.e. flood frequency analysis:
Optimisation runs smoothly and produce reasonable results for Mean and Standard Deviation for extreme values, normal and gamma distributions.
It stumbles however with log-normal distribution no matter parameters range. It produce blank screen i.e. no "depletion" red line.
What am I missing here?