Dear Mr. Simon Wood, dear list members, I am trying to fit a similar model with gam from mgcv compared to what I did with BayesX, and have discovered the relatively new possibility of incorporating user-defined matrices for quadratic penalties on parametric terms using the "paraPen" argument. This was really a very good idea!
However, I would like to constraint the coefficients belonging to one penalty matrix to sum to zero. So I would like to have the same centering constraint on user-defined penalized coefficient groups like it is implemented for the spline smoothing terms. The reason is that I have actually a factor coding different regions, and the penalty matrix results from the neighborhood structure in a Gaussian Markov Random Field (GMRF). So I can't choose one region as the reference category, because then the structure in the other regions would not contain the same information as before... Is there a way to constraint a group of coefficients to sum to zero? Thanks in advance, Daniel Sabanes ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
