https://github.com/cran/fields
Tip revision: 328f151e07864e976578f9134025cbfdb72eb2f3 authored by Doug Nychka on 19 July 2013, 23:45:29 UTC
version 6.8
version 6.8
Tip revision: 328f151
RadialBasis.R
RadialBasis <- function(d, M, dimension, derivative = 0) {
# compute the exponent for a thin-plate spline
# based on smoothness and dimension
p <- 2 * M - dimension
if (p <= 0) {
stop("M too small for thin plates spline, need: 2m-d >0")
}
if ((p - 1 < 0) & (derivative > 0)) {
stop("M is too small for derivatives, need: 2m-d < 1")
}
if (derivative == 0) {
if (dimension%%2 == 0) {
# factor of 2 from the log term
ifelse(d > 1e-14, radbas.constant(M, dimension) *
(d^p) * log(d), 0)
}
else {
radbas.constant(M, dimension) * (d^p)
}
}
else {
## find derivative
if (dimension%%2 == 0) {
# factor of 2 from the log term
ifelse(d > 1e-14, radbas.constant(M, dimension) *
(d^(p - 1)) * (p * log(d) + 1), 0)
}
else {
con <- radbas.constant(M, dimension) * p
con * (d^(p - 1))
}
}
##### should not get here!
}