Welcome to the Harris Geospatial product documentation center. Here you will find reference guides, help documents, and product libraries.
﻿

>  Docs Center  >  IDL Reference  >  Advanced Math and Stats  >  IMSL_BESSY

### IMSL_BESSY

IMSL_BESSY

The IMSL_BESSY function evaluates a Bessel function of the second kind with real order and real or complex parameters.

## Syntax

Result = IMSL_BESSY(order, z [, /DOUBLE] [, SEQUENCE=value])

## Return Value

The desired value of the modified Bessel function.

## Arguments

#### order

Real parameter specifying the desired order. The argument order must be greater than –1/2.

#### z

Real or complex parameter for which the Bessel function is to be evaluated.

## Keywords

#### DOUBLE

If present and nonzero, double precision is used.

#### SEQUENCE

If present and nonzero, a one-dimensional array of length n containing the values of the Bessel function through the series is returned by IMSL_BESSY, where n = NELEMENTS(SEQUENCE). The i-th element of this array is the Bessel function of order (order + i) at z for i = 0, ... (n – 1).

## Discussion

The IMSL_BESSY function evaluates a Bessel function of the second kind with real order and real or complex parameters. The data type of the returned value is always complex.

The Bessel function, Yv(z), is defined as follows:

This function is based on the code BESSCC of Thompson (1981) and Thompson and Barnett (1987). This code computes Yv(z) from the modified Bessel functions Iv(z) and Kv(z), using the following relation:

## Example

In this example, Y0.3 + v–1(1.2 + 0.5i), v = 1, ..., 4 is computed and printed.

`z = COMPLEX(1.2, .5)  FOR i = 0, 3 DO PM, IMSL_BESSY(i + .3, z)     ( -0.0131453, 0.379593)     (  -0.715533, 0.338082)     (   -1.04777, 0.794969)     (   -1.62487,  3.68447)  PM, IMSL_BESSY(.3, z, Sequence = 4), Title = ';With SEQUENCE:'  With SEQUENCE:     ( -0.0131453, 0.379593)     (  -0.715533, 0.338082)     (   -1.04777, 0.794969)     (   -1.62487,  3.68447)  `

## Version History

 6.4 Introduced

© 2018 Harris Geospatial Solutions, Inc. |  Legal