expint-package | R Documentation |
The exponential integrals E_1(x), E_2(x), E_n(x) and Ei(x), and the incomplete gamma function G(a, x) that is defined for negative values of its first argument.
The exponential integral
E_1(x) = int_x^Inf exp(-t)/t dt
and the incomplete gamma function
G(a, x) = int_x^Inf t^(a-1) exp(-t) dt
are closely related functions that arise in various fields of mathematics.
expint is a small package that provides R functions to compute the exponential integral and the incomplete gamma function.
Most conveniently for R package developers, the package also gives access to the underlying C workhorses through an API; see the package vignette for instructions.
The C routines are adapted versions of those of the GNU Scientific Library https://www.gnu.org/software/gsl/.
Vincent Goulet vincent.goulet@act.ulaval.ca
Abramowitz, M. and Stegun, I. A. (1972), Handbook of Mathematical Functions, Dover.
expint
for the exponential integral family of functions.
gammainc
for the incomplete gamma function.
vignette("expint")
for a detailed presentation of the package.
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