Hi, I am trying to find an elegant way to compute and store some frequently used matrices "on demand". The Matrix package already uses something like this for storing decompositions, but I don't know how to do it.
The actual context is the following: A list has information about a basis of a B-spline space (nodes, order) and gridpoints at which the basis functions would be evaluated (not necessarily the nodes). Something like this: bsplinegrid <- list(nodes=1:8,order=4,grid=seq(2,5,by=.2)) I need the design matrix (computed by splineDesign) for various derivatives (not necessarily known in advance), to be calculated by the function bsplinematrix <- function(bsplinegrid, deriv=0) { x <- bsplinegrid$grid Matrix(splineDesign(bslinegrid$knots, x, ord=basis$order, derivs = rep(deriv,length(x)))) } However, I don't want to call splineDesign all the time. A smart way would be storing the calculated matrices in a list inside bsplinegrid. Pseudocode would look like this: bsplinematrix <- function(bsplinegrid, deriv=0) { if (is.null(bsplinegrid$matrices[[deriv+1]])) { ## compute the matrix and put it in the list bsplinegrid$matrices, ## but not of the local copy } bsplinegrid$matrices[[deriv+1]] } My problem is that I don't know how to modify bsplinegrid$matrices outside the function -- assignment inside would only modify the local copy. Any help would be appreciated -- I wanted to learn how Matrix does it, but don't know how to display the source with s3 methods (getAnywhere doesn't work). Tamas ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel