NAG Library Routine Document
G01RTF returns the value of the derivative of the Landau density function, via the routine name.
|REAL (KIND=nag_wp) G01RTF
G01RTF evaluates an approximation to the derivative
of the Landau density function given by
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
can be used.
Kölbig K S and Schorr B (1984) A program package for the Landau distribution Comp. Phys. Comm. 31 97–111
- 1: X – REAL (KIND=nag_wp)Input
On entry: the argument of the function.
6 Error Indicators and Warnings
There are no failure exits from this routine.
At least significant digits are usually correct, but occasionally only . Such accuracy is normally considered to be adequate for applications in experimental physics.
Because of the asymptotic behaviour of ,
which is of the order of ,
underflow may occur on some machines when is moderately large and negative.
This example evaluates at , and prints the results.
9.1 Program Text
Program Text (g01rtfe.f90)
9.2 Program Data
Program Data (g01rtfe.d)
9.3 Program Results
Program Results (g01rtfe.r)