sim.rf.R
# 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
"sim.rf" <- function(obj) {
n <- obj$n
m <- obj$m
M <- obj$M
N <- obj$N
if (any(Re(obj$wght) < 0)) {
stop("FFT of covariance has negative\nvalues")
}
z <- fft(matrix(rnorm(N * M), ncol = N, nrow = M))
Re(fft(sqrt(obj$wght) * z, inverse = TRUE))[1:m, 1:n]/sqrt(M *
N)
}