https://github.com/cran/fields
Tip revision: 8182a9a01e5ac26047a101825b76f85617a37cf8 authored by Doug Nychka on 06 February 2009, 21:36:12 UTC
version 5.02
version 5.02
Tip revision: 8182a9a
bisection.search.R
# fields, Tools for spatial data
# Copyright 2004-2007, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html
"bisection.search" <-
function (x1, x2, f, tol = 1e-07, niter = 25, f.extra = NA, upcross.level = 0)
{
f1 <- f(x1, f.extra) - upcross.level
f2 <- f(x2, f.extra) - upcross.level
if (f1 > f2)
stop(" f1 must be < f2 ")
iter <- niter
for (k in 1:niter) {
xm <- (x1 + x2)/2
fm <- f(xm, f.extra) - upcross.level
if (fm < 0) {
x1 <- xm
f1 <- fm
}
else {
x2 <- xm
f2 <- fm
}
if (abs(fm) < tol) {
iter <- k
break
}
}
xm <- (x1 + x2)/2
fm <- f(xm, f.extra) - upcross.level
list(x = xm, fm = fm, iter = iter)
}