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# expint

Exponential integral

Y = expint(X)

## Definitions

The exponential integral computed by this function is defined as

Another common definition of the exponential integral function is the Cauchy principal value integral

which, for real positive x, is related to expint as

${E}_{1}\left(-x\right)=-\text{Ei}\left(x\right)-i\pi$

## Description

Y = expint(X) evaluates the exponential integral for each element of X.

## References

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