SAS/C Library Reference, Vol. 1

yn -- Bessel Function of the Second Kind, Order n

SYNOPSIS

 #include <lcmath.h>

 double yn(int n, double x);

DESCRIPTION

yn computes the order n Bessel function of the second kind of the value x.

The CPU time required to compute the Bessel function increases with increasing values for n. For very large values of n, the time can be quite large.

RETURN VALUE

yn returns the order n Bessel function of the second kind of the argument x, provided that this value is computable.

DIAGNOSTICS

If the value of x is 0.0, a diagnostic message is written to the standard error file (stderr) and the function returns -HUGE_VAL, the largest negative floating-point number that can be represented.

If the magnitude of x is too large (|x| >= 6.7465e9), yn returns 0.0. In this case, the message "total loss of significance" is written to stderr.

If the magnitude of x is too close to 0, an overflow error occurs during computation of yn. The limiting value for x depends on the value for n. If n is 1, the limiting value is approximately 8.032e-77. The limiting value increases with increasing values of n. When x is too small, a diagnostic message is written to stderr, and yn returns -HUGE_VAL.

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

EXAMPLE

This example computes the Bessel function of the second kind, of order 7 at
x = 5:

  #include <stdio.h>
  #include <lcmath.h>

  main()
  {
     double y;
     y = yn(7, 5.);
     printf("yn(7, 5.) = %lfn", y);
  }

RELATED FUNCTIONS

j0, j1, jn, _matherr, y0, y1