Hi, I am trying to get the basis matrix and penalty matrix for natural cubic splines. I found R function "ns" can generate the B-spline basis matrix for a natural cubic spline; and "bsplinepen" can compute the penalty matrix for functions expressed in terms of a B-spline basis. However, these two functions seem not compatible. I could not get the penalty matrix by "bsplinepen" using the basis matrix generated from "ns". Anyone knows any compatible functions to give the basis matrix and penalty matrix for natural cubic splines? Thanks a lot! Wei