bisection.search.r
# fields, Tools for spatial data
# Copyright 2004-2011, 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)
}