# fields, Tools for spatial data
# Copyright 2004-2013, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html
fields.derivative.poly <- function(x, m, dcoef) {
    # dimension of x locations
    # goal is find partial derivative matrix
    d <- ncol(x)
    out <- fields.mkpoly(rbind(x[1, ]), m)
    ptab <- attr(out, "ptab")
    if (nrow(ptab) != length(dcoef)) {
        stop(" rows of ptab not equal to length of dcoef")
    }
    hold <- matrix(NA, ncol = d, nrow = nrow(x))
    for (k in 1:d) {
        nonzero <- ptab[, k] != 0
        ptemp <- matrix(ptab[nonzero, ], ncol = d)
        dtemp <- dcoef[nonzero]
        dtemp <- dtemp * ptemp[, k]
        ptemp[, k] <- ptemp[, k] - 1
        hold[, k] <- fields.evlpoly2(x, dtemp, ptemp)
    }
    return(hold)
}