Optimizing Code for Efficient Linear Interpolation in R
Optimized Code
The optimized code is as follows:
pip <- function(ps, interp = NULL, breakpoints = NULL) { if (missing(interp)) { interp <- approx(x = c(ps[1,"x"], ps[nrow(ps),"x"]), y = c(ps[1,"y"],ps[nrow(ps),"y"]), n = nrow(ps)) interp <- do.call(cbind, interp) breakpoints <- c(1, nrow(ps)) } else { ds <- sqrt(rowSums((ps - interp)^2)) # close by euclidean distance ind <- which.max(ds) ends <- c(min(ind-breakpoints[breakpoints<ind]), min(breakpoints[breakpoints>ind]-ind)) leg1 <- approx(x = c(ps[ind-ends[1],"x"], ps[ind,"x"]), y = c(ps[ind-ends[1],"y"], ps[ind,"y"]), n = ends[1]+1) leg2 <- approx(x = c(ps[ind,"x"], ps[ind+ends[2],"x"]), y = c(ps[ind,"y"], ps[ind+ends[2],"y"]), n = ends[2]) interp[(ind-ends[1]):ind, "y"] <- leg1$y interp[(ind+1):(ind+ends[2]), "y"] <- leg2$y breakpoints <- c(breakpoints, ind) } list(interp = interp, breakpoints = breakpoints) } constructPIP <- function(ps, times = 10) { res <- pip(ps) for (i in 2:times) { res <- pip(ps, res$interp, res$breakpoints) } res } Explanation
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