s18cc returns a value of the scaled modified Bessel function exK0x.

Syntax

C#
public static double s18cc(
	double x,
	out int ifail
)
Visual Basic
Public Shared Function s18cc ( _
	x As Double, _
	<OutAttribute> ByRef ifail As Integer _
) As Double
Visual C++
public:
static double s18cc(
	double x, 
	[OutAttribute] int% ifail
)
F#
static member s18cc : 
        x : float * 
        ifail : int byref -> float 

Parameters

x
Type: System..::..Double
On entry: the argument x of the function.
Constraint: x>0.0.
ifail
Type: System..::..Int32%
On exit: ifail=0 unless the method detects an error or a warning has been flagged (see [Error Indicators and Warnings]).

Return Value

s18cc returns a value of the scaled modified Bessel function exK0x.

Description

s18cc evaluates an approximation to exK0x, where K0 is a modified Bessel function of the second kind. The scaling factor ex removes most of the variation in K0x.
The method uses the same Chebyshev expansions as s18ac, which returns the unscaled value of K0x.

References

Abramowitz M and Stegun I A (1972) Handbook of Mathematical Functions (3rd Edition) Dover Publications

Error Indicators and Warnings

Errors or warnings detected by the method:
ifail=1
On entry, x0.0, K0 is undefined.
On failure, s18cc returns zero.
ifail=-9000
An error occured, see message report.

Accuracy

Relative errors in the argument are attenuated when propagated into the function value. When the accuracy of the argument is essentially limited by the machine precision, the accuracy of the function value will be similarly limited by at most a small multiple of the machine precision.

Parallelism and Performance

None.

Further Comments

None.

Example

This example reads values of the argument x from a file, evaluates the function at each value of x and prints the results.

Example program (C#): s18cce.cs

Example program data: s18cce.d

Example program results: s18cce.r

See Also