R: Exponential Integral and Incomplete Gamma Function

expint-package {expint} | R Documentation

## Exponential Integral and Incomplete Gamma Function

### Description

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.

### Details

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/.

### Author(s)

Vincent Goulet vincent.goulet@act.ulaval.ca

### 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.

[Package expint version 0.1-7 Index]