Learn R Programming

expint (version 0.1-8)

expint-package: tools:::Rd_package_title("expint")

Description

The exponential integrals \(E_1(x)\), \(E_2(x)\), \(E_n(x)\) and \(Ei(x)\), and the incomplete gamma function \(\Gamma(a, x)\) that is defined for negative values of its first argument.

Arguments

Author

Vincent Goulet vincent.goulet@act.ulaval.ca

Details

The exponential integral $$ E_1(x) = \int_x^\infty \frac{e^{-t}}{t}\, dt$$ and the incomplete gamma function $$ \Gamma(a, x) = \int_x^\infty t^{a-1} e^{-t}\, dt$$ 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/.

References

Abramowitz, M. and Stegun, I. A. (1972), Handbook of Mathematical Functions, Dover.

See Also

expint for the exponential integral family of functions.

gammainc for the incomplete gamma function.

vignette("expint") for a detailed presentation of the package.