s18de {NAGFWrappers} R Documentation

## s18de: Modified Bessel functions I_nu + a(z), real a >= 0, complex z, nu = 0 , 1 , 2 , . . .

### Description

s18de returns a sequence of values for the modified Bessel functions I_ν + n(z) for complex z, non-negative ν and n = 0 , 1 , . . . , N - 1, with an option for exponential scaling.

### Usage

```s18de(fnu, z, n, scal)
```

### Arguments

 `fnu` double ν, the order of the first member of the sequence of functions. `z` complex The argument z of the functions. `n` integer N, the number of members required in the sequence I_ν(z) , I_ν + 1(z) , . . . , I_ν + N - 1(z). `scal` string The scaling option. scal='U': The results are returned unscaled. scal='S': The results are returned scaled by the factor e^ - abs(Re(z)).

### Details

R interface to the NAG Fortran routine S18DEF.

### Value

 `CY` complex array The N required function values: cy[i] contains I_ν + i - 1(z) for i=1 . . . N. `NZ` integer The number of components of cy that are set to zero due to underflow. `IFAIL` integer ifail =0 unless the function detects an error or a warning has been flagged (see the Errors section in Fortran library documentation).

NAG

### Examples

```
ifail<-0

fnu<-0

z<-complex(1,0.3,-0.4)

n<-2

scal<-'U'

s18de(fnu,z,n,scal)

```

[Package NAGFWrappers version 24.0 Index]