Nothing

```
# fields is a package for analysis of spatial data written for
# the R software environment .
# Copyright (C) 2018
# University Corporation for Atmospheric Research (UCAR)
# Contact: Douglas Nychka, nychka@ucar.edu,
# National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the R software environment if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
# or see http://www.r-project.org/Licenses/GPL-2
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)
}
```

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