KELVIN_BER0 Function
Evaluates the Kelvin function of the first kind, ber, of order zero.
Usage
result = KELVIN_BER0(x)
Input Parameters
x—Argument for which the function value is desired.
Returned Value
result—The value of the Kelvin function of the first kind, ber, 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 first kind, ber, of order zero evaluated at x is computed.
Discussion
The Kelvin function ber0(x) is defined to be 
. The Bessel function J0(x) is defined:
. The Bessel function J0(x) is defined:
If the keyword Derivative is set, the function ber0'(x) is defined to be
If |x| > 119, NaN is returned.
The function KELVIN_BER0 is based on the work of Burgoyne (1963).
Example
In this example, ber0 (0.4) and ber0' (0.6) are evaluated.
PRINT, KELVIN_BER0(0.4)
; PV-WAVE prints: 0.999600
PRINT, KELVIN_BER0(0.6, /DERIVATIVE)
; PV-WAVE prints: -0.0134985
