Sets up the necessary backend for the WN process.

`WN(sigma2 = NULL)`

- sigma2
A

`double`

value for the variance, \(\sigma ^2\), of a WN process.

An S3 object with called ts.model with the following structure:

- process.desc
Used in summary: "WN"

- theta
\(\sigma\)

- plength
Number of Parameters

String containing simplified model

- desc
y desc replicated x times

- obj.desc
Depth of Parameters e.g. list(1)

- starting
Guess Starting values? TRUE or FALSE (e.g. specified value)

In this process, \(Y_t\) is iid from a zero mean normal distribution with variance \(\sigma^2\)

```
WN()
WN(sigma2=3.4)
```