SAS/C Library Reference, Vol. 1

gamma -- Compute the Logarithm of the Gamma Function

SYNOPSIS

 #include <lcmath.h>

 double gamma(double x);

DESCRIPTION

gamma computes the logarithm of the gamma function of its argument x. The value returned by gamma is defined by this equation:

RETURN VALUE

gamma returns the logarithm of the gamma function of its argument.

DIAGNOSTICS

The run-time library writes an error message to the standard error file (stderr) if x is a negative number or 0. In this case, the function returns HUGE_VAL, the largest positive floating-point number that can be represented. Also, the run-time library writes an error message to the standard error file (stderr) if x is greater than 0.42686124520937873e74 in scientific notation. In this case, the function returns HUGE_VAL, the largest positive floating-point number that can be represented.

If an error occurs in gamma, the _matherr routine is called. You can supply your own version of _matherr to suppress the diagnostic message or modify the value returned.

PORTABILITY

gamma is portable to many, but not all, non UNIX C implementations.

EXAMPLE

This example computes the logarithm of the gamma function using gamma:

  #include <stdio.h>
  #include <lcmath.h>
  #define SVECTOR .7854

  main()
  {
     double lgamv;
     lgamv = gamma(SVECTOR);
     printf("gamma(%f) = %fn", SVECTOR, lgamv);
  }

RELATED FUNCTIONS

_matherr