IMSL_KELVIN_BEI0

Syntax | Return Value | Arguments | Keywords | Discussion | Example | Version History

The IMSL_KELVIN_BEI0 function evaluates the Kelvin function of the first kind, bei, of order zero.

Note
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Syntax

Result = IMSL_KELVIN_BEI0(x [, DERIVATIVE=value] [, /DOUBLE])

Return Value

The value of the Kelvin function of the first kind, bei, 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 first kind, bei, of order zero evaluated at x is computed.

DOUBLE

If present and nonzero, double precision is used.

Discussion

The Kelvin function bie₀(x) is defined to be . The Bessel function J₀(x) is defined:

In IMSL_KELVIN_BEI0, x must be less than 119.

If the keyword DERIVATIVE is set, the function bei₀′(x) is defined to be:

If the keyword DERIVATIVE is set and |x| > 119, NaN is returned.

The IMSL_KELVIN_BEI0 function is based on the work of Burgoyne (1963).

Example

In this example, bei₀(0.4) and bei₀′(0.6) are evaluated.

PRINT, IMSL_KELVIN_BEI0(0.4) 
    0.0399982 
PRINT, IMSL_KELVIN_BEI0(0.6, /DERIVATIVE) 
     0.299798 

Version History