NAG CL Interface
g01ptc (pdf_​landau_​moment1)

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1 Purpose

g01ptc returns the value of the first moment Φ1(x) of the Landau density function.

2 Specification

#include <nag.h>
double  g01ptc (double x)
The function may be called by the names: g01ptc, nag_stat_pdf_landau_moment1 or nag_moment_1_landau.

3 Description

g01ptc evaluates an approximation to the first moment Φ1 (x) of the Landau density function given by
Φ1(x)=1Φ(x) -xλϕ(λ)dλ,  
where ϕ(λ) is described in g01mtc, using piecewise approximation by rational functions. Further details can be found in Kölbig and Schorr (1984).
To obtain the value of Φ2(x), g01qtc can be used.

4 References

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

5 Arguments

1: x double Input
On entry: the argument x of the function.

6 Error Indicators and Warnings


7 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.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
g01ptc is not threaded in any implementation.

9 Further Comments


10 Example

This example evaluates Φ1(x) at x=0.5, and prints the results.

10.1 Program Text

Program Text (g01ptce.c)

10.2 Program Data

Program Data (g01ptce.d)

10.3 Program Results

Program Results (g01ptce.r)