G01PTF (PDF version)
G01 Chapter Contents
G01 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

G01PTF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

 Contents

    1  Purpose
    7  Accuracy

1  Purpose

G01PTF returns the value of the first moment Φ1x of the Landau density function, via the routine name.

2  Specification

FUNCTION G01PTF ( X)
REAL (KIND=nag_wp) G01PTF
REAL (KIND=nag_wp)  X

3  Description

G01PTF evaluates an approximation to the first moment Φ1 x of the Landau density function given by
Φ1x=1Φx -xλϕλdλ,  
where ϕλ is described in G01MTF, using piecewise approximation by rational functions. Further details can be found in Kölbig and Schorr (1984).
To obtain the value of Φ2x, G01QTF 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  Parameters

1:     X – REAL (KIND=nag_wp)Input
On entry: the argument x of the function.

6  Error Indicators and Warnings

None.

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

Not applicable.

9  Further Comments

None.

10  Example

This example evaluates Φ1x at x=0.5, and prints the results.

10.1  Program Text

Program Text (g01ptfe.f90)

10.2  Program Data

Program Data (g01ptfe.d)

10.3  Program Results

Program Results (g01ptfe.r)


G01PTF (PDF version)
G01 Chapter Contents
G01 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2015