Dear list, I'm currently trying to write a new R package to model spatial extremes. In particular, for a model fitting procedure, I'd like to use flexible response surfaces (like linear models, splines, ...) for the parameters of my model. Following this idea, I'd like to allow "a new interpretation" of an R formula given by the user, like y ~ x1 + rb(x2, knots, degree, penalty) where x1, x2 are covariates and rb stands for using a radial basis smooth splines with given knots, degree and penalty coefficient. Such "new formula" should then provide the appropriate design matrix. I know that existing packages have done this way too - e.g. mgcv; but their codes are quite hard to understand - for me I mean. Does anyone can provide some useful guidelines to do this kind of stuffs or provide more readable codes? In advance, thank you Best, Mathieu -- Institute of Mathematics Ecole Polytechnique F?d?rale de Lausanne STAT-IMA-FSB-EPFL, Station 8 CH-1015 Lausanne Switzerland http://stat.epfl.ch/ Tel: + 41 (0)21 693 7907