Don't care about my previous email. I have eventually modified the function and it gives me now the series of the residuals. Hence, I can use the following commands:
Unconstrained maximum: mle logl = - 0.5*ln(2*pi) - ln(sigma) - 0.5*(e/sigma)^2 series e = pstr_cres(y,X,q,gamma,c,m,Z) params gamma c sigma end mle Constrained maximum: matrix ac = atanh((2*c-c_max-c_min)./(c_max-c_min)) matrix lg = ln(gamma) mle logl = - 0.5*ln(2*pi) - ln(sigma) - 0.5*(e/sigma)^2 series e = pstr_cres(y,X,q,gamma,c,m,Z) matrix gamma = exp(lg) matrix c = c_min + 0.5*(tanh(ac) + 1)*(c_max-c_min) params lg ac sigma end mle Thanks Giuseppe On Thu, 2011-10-27 at 09:57 +0200, Giuseppe Vittucci wrote: > Still on the mle command. > The argument of the mle command in gretl is actually the log-L > contributions and not the Log-L. > Clearly every combination of parameters that maximize the latter also > maximize the former. > So, as far as the point estimates of the parameters are concerned, it > does not really matters which one is used. > > So far I have used mle simply as a maximization BFGS method, and I was > not looking at the covariance or the other ancillary statistics. > > In my case working directly with the log-likelihood is much easier cause > I have a quite complex function that returns the SSR and I use it > directly in the command. > In case of homoscedastic normally distributed residuals, the Log-L is > indeed just: > > Log-L = -n/2*(ln (ssr/n) + 1 + ln 2pi) > > and I can use my function directly in the formula. > On the contrary, working directly with the log-L contributions is not > straightforward in my case. > > I would like to know if I could use the covariance matrix and the other > statistics generated by the program (in particular the information > criteria), if, instead of using the Log-L contributions, I simply divide > the Log-L by n. > > As far as the covariance is concerned, likely I cannot use the matrix > calculated from the outer product of the gradient, but can I use the > Hessian? > > Thanks a lot > Giuseppe