KELVIN_KER0 Function
Evaluates the Kelvin function of the second kind, ker, of order zero.
Usage
result = KELVIN_KER0(x)
Input Parameters
x—Argument for which the function value is desired.
Returned Value
result—The value of the Kelvin function of the second kind, ker, of order zero evaluated at x.
Input Keywords
Double—If present and nonzero, double precision is used.
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.
Discussion
The modified Kelvin function ker0(x) is defined to be 
. The Bessel function K0(x) is defined:
. 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 ≥ 119, then zero is returned.
The function KELVIN_KER0 is based on the work of Burgoyne (1963).
Example
In this example, ker0(0.4) and ker0'(0.6) are evaluated.
PRINT, KELVIN_KER0(0.4)
; PV-WAVE prints: 1.06262
PRINT, KELVIN_KER0(0.6, /DERIVATIVE)
; PV-WAVE prints: -1.45654
