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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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