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#
# fields is a package for analysis of spatial data written for
# the R software environment.
# Copyright (C) 2024 Colorado School of Mines
# 1500 Illinois St., Golden, CO 80401
# Contact: Douglas Nychka, douglasnychka@gmail.com,
#
# 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
##END HEADER
"fields.x.to.grid" <- function(x, nx = 80, ny = 80, xy = c(1, 2)) {
if (is.null(x)) {
stop("Need a an x matrix to determine ranges for grid")
}
M <- ncol(x)
if (M == 1) {
#special case of 1-D
grid.list <- list(x = seq(min(x), max(x), length.out = nx))
}
else{
grid.list <- as.list(1:M)
# add columns names
names(grid.list) <- dimnames(x)[[2]]
# cruise through x dimensions and find medians.
for (k in 1:M) {
grid.list[[k]] <- median(x[, k])
}
#
#
# overwrite with sequences for the two variables of surface
xr <- range(x[, xy[1]])
yr <- range(x[, xy[2]])
grid.list[[xy[1]]] <- seq(xr[1], xr[2], , nx)
grid.list[[xy[2]]] <- seq(yr[1], yr[2], , ny)
}
return(grid.list)
}
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