NAG Library Function Document
nag_prob_der_landau (g01rtc) returns the value of the derivative of the Landau density function.
||nag_prob_der_landau (double x)
evaluates an approximation to the derivative
of the Landau density function given by
is described in nag_prob_density_landau (g01mtc)
, using piecewise approximation by rational functions. Further details can be found in Kölbig and Schorr (1984)
To obtain the value of
, nag_prob_density_landau (g01mtc)
can be used.
Kölbig K S and Schorr B (1984) A program package for the Landau distribution Comp. Phys. Comm. 31 97–111
On entry: the argument of the function.
Error Indicators and Warnings
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.
Parallelism and Performance
nag_prob_der_landau (g01rtc) is not threaded in any implementation.
This example evaluates at , and prints the results.
Program Text (g01rtce.c)
Program Data (g01rtce.d)
Program Results (g01rtce.r)