A double value for the variance, $sigma^2[gm]$, of a WN process.
Value
An S3 object with called ts.model with the following structure:
process.desc
Used in summary: "BETA","SIGMA2"
theta
$beta$, $sigma^2[gm]$
plength
Number of Parameters
desc
"GM"
obj.desc
Depth of Parameters e.g. list(1,1)
starting
Guess Starting values? TRUE or FALSE (e.g. specified value)
Details
When supplying values for $beta$ and $sigma^2[gm]$,
these parameters should be of a GM process and NOT of an AR1. That is,
do not supply AR1 parameters such as $phi$, $sigma^2$.
Internally, GM parameters are converted to AR1 using the `freq`
supplied when creating data objects (imu, gts)
or specifying a `freq` parameter in gmwm or gmwm.imu.
The `freq` of a data object takes precedence over the `freq` set when modeling.