g01et returns the value of the Landau distribution function Φλ.

Syntax

C#
public static double g01et(
	double x
)
Visual Basic
Public Shared Function g01et ( _
	x As Double _
) As Double
Visual C++
public:
static double g01et(
	double x
)
F#
static member g01et : 
        x : float -> float 

Parameters

x
Type: System..::..Double
On entry: the argument λ of the function.

Return Value

g01et returns the value of the Landau distribution function Φλ.

Description

g01et evaluates an approximation to the Landau distribution function Φλ given by
Φλ=-λϕλdλ,
where ϕλ is described in g01mt, using piecewise approximation by rational functions. Further details can be found in Kölbig and Schorr (1984).

References

Kölbig K S and Schorr B (1984) A program package for the Landau distribution Comp. Phys. Comm. 31 97–111

Error Indicators and Warnings

There are no failure exits from this routine.

Accuracy

At least 7 significant digits are usually correct, but occasionally only 6. Such accuracy is normally considered to be adequate for applications in experimental physics.
Because of the asymptotic behaviour of Φλ, which is of the order of exp-exp-λ, underflow may occur on some machines when λ is moderately large and negative.

Parallelism and Performance

None.

Further Comments

None.

Example

This example evaluates Φλ at λ=0.5, and prints the results.

Example program (C#): g01ete.cs

Example program data: g01ete.d

Example program results: g01ete.r

See Also