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IMSL_KELVIN_KER0

IMSL_KELVIN_KER0

The KELVIN_KERO function evaluates the Kelvin function of the second kind, ker, of order zero.



Syntax


Result = IMSL_KELVIN_KER0(x [, DERIVATIVE=value] [, /DOUBLE])

Return Value


The value of the Kelvin function of the second kind, ker, of order zero evaluated at x.

Arguments


x

Argument for which the function value is desired.

Keywords


DERIVATIVE

If present and nonzero, then the derivative of the Kelvin function of the second kind, ker, of order zero evaluated at x is computed.

DOUBLE

If present and nonzero, double precision is used.

Discussion


The modified Kelvin function ker0(x) is defined to be ¬K0(xepi/4). The Bessel function K0(x) is defined:

If the keyword DERIVATIVE is set, the function ker0¢(x) is defined to be:

If x < 0, NaN (Not a Number) is returned. If x ³ 119, then zero is returned.

The IMSL_KELVIN_KER0 function is based on the work of Burgoyne (1963).

Example


In this example, ker0(0.4) and ker0¢(0.6) are evaluated.

PRINT, IMSL_KELVIN_KER0(0.4)  
1.06262
PRINT, IMSL_KELVIN_KER0(0.6, /DERIVATIVE)
-1.45654

Version History


6.4
Introduced



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