expint

Purpose

Exponential integral.

Y = expint(X)

Y = expint(X) evaluates the exponential integral

for each element of X.

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]):

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