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
circulantEmbeddingSetup <- function(
grid, M = NULL, cov.function="stationary.cov", cov.args=NULL, ...) {
#
# if cov object is missing then create
# basically need to enlarge domain and find the FFT of the
# covariance
#
cov.args<-c( cov.args, list(...))
L<- length( grid)
dx<- rep( NA, L)
m<- rep( NA, L)
for( i in 1:L){
gridTmp<- grid[[i]]
dx[i]<- gridTmp[2]- gridTmp[1]
m[i]<- length( gridTmp)
}
# M is the larger grid size the includes m should be at least 2*m for embedding to be exact.
if( is.null(M)){
M<- rep( NA, L)
for( i in 1:L){
M[i]<- 2**(ceiling(log2(2*m[i]) ))
}
}
if( length(M)!= length( grid)){
stop("M should be same length as grid")
}
# create the larger multigrid using M
bigIndex<- makeMultiIndex( M)
MCenter<- round( M/2)
center<- rbind( MCenter* dx)
# this might be made more effficient anothe way ....
bigGrid<- array( NA, dim(bigIndex) )
for( i in 1:L){
bigGrid[,i]<- bigIndex[,i]*dx[i]
}
#
# here is where the actual covariance form is used
# note passed arguments from call for parameters etc.
#
out<- do.call(cov.function, c(cov.args, list(x1 = bigGrid, x2 = center)))
# coerce to an array note that this depends on the bigIndex varying in the right way
out<- array( c(out),M)
temp <- array( 0, M)
#
# a simple way to normalize. This could be avoided by
# translating image from the center ...
#
# add to the middle point in the array -- matches the center from above
temp[rbind( MCenter)] <- 1
wght <- fft(out)/(fft(temp) * prod(M))
#
# wght is the discrete FFT for the covariance suitable for fast
# multiplication by convolution.
#
covObject <- list(m = m, grid = grid, dx=dx, M = M,
wght = wght, call = match.call())
return( covObject)
}
```

**Any scripts or data that you put into this service are public.**

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.