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### IMSL_KELVIN_BER0

IMSL_KELVIN_BER0

The IMSL_KELVIN_BER0 function evaluates the Kelvin function of the first kind, ber, of order zero.

This routine requires an IDL Advanced Math and Stats license. For more information, contact your sales or technical support representative.

The Kelvin function ber0(x) is defined to be ¬J0(xe3pi/4). 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 IMSL_KELVIN_BER0 function is based on the work of Burgoyne (1963).

## Example

In this example, ber0 (0.4) and ber0′ (0.6) are evaluated.

`PRINT, IMSL_KELVIN_BER0(0.4)`
`  0.999600`
`PRINT, IMSL_KELVIN_BER0(0.6, /DERIVATIVE)`
`  -0.0134985`

## Syntax

Result = IMSL_KELVIN_BER0(X [, DERIVATIVE=value] [, /DOUBLE])

## Return Value

The value of the Kelvin function of the first kind, ber, of order zero evaluated at x.

## Arguments

### X

Argument for which the function value is desired.

## Keywords

### DERIVATIVE (optional)

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

### DOUBLE (optional)

If present and nonzero, then double precision is used.

## Version History

 6.4 Introduced