Computes the principal value of the exponential integral.
Namespace: Meta.Numerics.FunctionsAssembly: Meta.Numerics (in Meta.Numerics.dll) Version: 2.1.0.0 (2.1.0.0)
Syntax
| C# | Visual Basic | Visual C++ | F# |
Parameters
- x
- Double
The argument, which must be non-negative.
Return Value
The value of Ei(x).
Remarks
The function Ei(x) appears in the evaluation of some indefinite integrals involving exponents and in number theory in the approximation li(x) = Ei(ln x) to the cumulative distribution of primes.
It is related to the real part of the exponential integral for negative arguments by E1(-x ± iε) = -Ei(x) ∓ iπ.
Exceptions
| Exception | Condition |
|---|---|
| System..::..ArgumentOutOfRangeException | x is negative. |