https://github.com/cran/fields
Tip revision: d5f2ee6b54d2b8ab0c2a433f190233e9dde427e8 authored by Douglas Nychka on 04 February 2020, 15:30:02 UTC
version 10.3
version 10.3
Tip revision: d5f2ee6
rdist.earth.R
# 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
"rdist.earth" <- function(x1, x2=NULL, miles = TRUE, R = NULL) {
if (is.null(R)) {
if (miles)
R <- 3963.34
else R <- 6378.388
}
coslat1 <- cos((x1[, 2] * pi)/180)
sinlat1 <- sin((x1[, 2] * pi)/180)
coslon1 <- cos((x1[, 1] * pi)/180)
sinlon1 <- sin((x1[, 1] * pi)/180)
if (is.null(x2)) {
pp <- cbind(coslat1 * coslon1, coslat1 * sinlon1, sinlat1) %*%
t(cbind(coslat1 * coslon1, coslat1 * sinlon1, sinlat1))
return(R * acos(ifelse(abs(pp) > 1, 1 * sign(pp), pp)))
}
else {
coslat2 <- cos((x2[, 2] * pi)/180)
sinlat2 <- sin((x2[, 2] * pi)/180)
coslon2 <- cos((x2[, 1] * pi)/180)
sinlon2 <- sin((x2[, 1] * pi)/180)
pp <- cbind(coslat1 * coslon1, coslat1 * sinlon1, sinlat1) %*%
t(cbind(coslat2 * coslon2, coslat2 * sinlon2, sinlat2))
return(R * acos(ifelse(abs(pp) > 1, 1 * sign(pp), pp)))
}
}