log1mexp {DPQ} | R Documentation |
Compute f(a) = log(1 - exp(-a)) quickly and numerically accurately.
log1mexp()
is simple pure R code;
log1mexpC()
is an interface to R C API (‘Rmathlib’)
function.
log1pexpC()
is an interface to R C API (‘Rmathlib’)
double
function log1pexp()
which computes log(1 + exp(x)), accurately, notably for large x, say, x > 720.
log1mexp (x) log1mexpC(x) log1pexpC(x)
x |
numeric vector of positive values. |
Martin Maechler
Martin Mächler (2012). Accurately Computing \log(1-\exp(-|a|)); https://CRAN.R-project.org/package=Rmpfr/vignettes/log1mexp-note.pdf.
The log1mexp()
function in CRAN package copula,
and the corresponding vignette (in the ‘References’).
l1m.xy <- curve(log1mexp(x), -10, 10, n=1001) stopifnot(with(l1m.xy, all.equal(y, log1mexpC(x))))