# expint

## Purpose

Exponential integral.

## Synopsis

    Y = expint(X)

## Description

`Y = expint(X)` evaluates the exponential integral

for each element of `X`.

## Algorithm

For elements of `X` in the range [-38,2], `expint` uses a series expansion representation (equation 5.1.10 in [1]):

For all other elements of `X`, `expint` uses a continued fraction representation (equation 5.1.22 in [1]):

## References

[1] Abramowitz, M. and I. A. Stegun. Handbook of Mathematical Functions. Chapter 5, New York: Dover Publications, 1965.

(c) Copyright 1994 by The MathWorks, Inc.