Hi, I have a function (negative log-likelihood) which i want to minimize , and find the parameters value. The function is in the form of
f(n)=log(a*exp(-t/b))+log((1-a)*exp(-t/c))+log(a*exp(-t/b)+(1-a)*exp(-t/c))+.........(more terms in the same form)

t is time, and which is knowable.

Would you please tell me whether powell can be used to minimize this function?:)