BuildSysPro.IBPSA.Utilities.Math.Functions.exponentialIntegralE1

# .BuildSysPro.IBPSA.Utilities.Math.Functions.exponentialIntegralE1

Exponential integral, E1

## Information

Evaluates the exponential integral (E1), based on the polynomial and rational approximations of Abramowitz and Stegun (1964).

#### References

Abramowitz, Milton, and Irene A. Stegun. Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables. National Bureau of Standards. (1964): 1046 p.

#### Interface

>     function exponentialIntegralE1
>       extends Modelica.Icons.Function;
>       input Real x "Independent variable";
>       output Real E1 "Exponential integral E1(x)";
>     end exponentialIntegralE1;

## Revisions

- July 16, 2018 by Michael Wetter:
  Inlined function.
- March 21, 2018 by Massimo Cimmino:
  First implementation.

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