Thanks for the awesome package. Cristian.
For implementation of WTP Space models, having reasonable starting values may be critical. My attempt to estimate my own data resulted in convergence issue: " Nonpositive definiteness in Cholesky factorization in formt; refresh the lbfgs memory and restart the iteration." The log likelihood is poor, indicating that the algorithm was stuck somewhere.
My intuition is that with proper starting values, the issues of local maxima or flat regions can be tackled. Is it possible to provide starting values to the procedure?
Further, Greene and Hensher (2010; Trasnportation Part D) and Fiebig et al. (2010; Marketing Science) have shown that WTP Space can be implemented with GMNL. The advantage of that is that the price parameter follows a log normal distribution. I wonder how the present set up of xlogit compares to/allow this specification.
Again, thanks for the awesome package. Xlogit is unrivalled in speed. It would be great to complete it with more useful features. This is a lot to ask. I would help if I can overcome the learning curve of programming it.
Thanks for the awesome package. Cristian.
For implementation of WTP Space models, having reasonable starting values may be critical. My attempt to estimate my own data resulted in convergence issue: " Nonpositive definiteness in Cholesky factorization in formt; refresh the lbfgs memory and restart the iteration." The log likelihood is poor, indicating that the algorithm was stuck somewhere.
My intuition is that with proper starting values, the issues of local maxima or flat regions can be tackled. Is it possible to provide starting values to the procedure?
Further, Greene and Hensher (2010; Trasnportation Part D) and Fiebig et al. (2010; Marketing Science) have shown that WTP Space can be implemented with GMNL. The advantage of that is that the price parameter follows a log normal distribution. I wonder how the present set up of xlogit compares to/allow this specification.
Again, thanks for the awesome package. Xlogit is unrivalled in speed. It would be great to complete it with more useful features. This is a lot to ask. I would help if I can overcome the learning curve of programming it.