s18ce returns a value of the scaled modified Bessel function e-xI0x.


public static double s18ce(
	double x
Visual Basic
Public Shared Function s18ce ( _
	x As Double _
) As Double
Visual C++
static double s18ce(
	double x
static member s18ce : 
        x : float -> float 


Type: System..::..Double
On entry: the argument x of the function.

Return Value

s18ce returns a value of the scaled modified Bessel function e-xI0x.


s18ce evaluates an approximation to e-xI0x, where I0 is a modified Bessel function of the first kind. The scaling factor e-x removes most of the variation in I0x.
The method uses the same Chebyshev expansions as s18ae, which returns the unscaled value of I0x.


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

Error Indicators and Warnings

There are no actual failure exits from this method. _ifail is always set to zero. This parameter is included for compatibility with other methods in this chapter.


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


Further Comments



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#): s18cee.cs

Example program data: s18cee.d

Example program results: s18cee.r

See Also