The no. of rolling forecasts to create beyond the first one.
external.forecasts
A list with a matrix object of the external lagged forecasts (if used). These
must contain (n.roll+1) x n.ahead forecasts.
cluster
A cluster object created by calling makeCluster from
the parallel package. If it is not NULL, then this will be used for parallel
estimation (remember to stop the cluster on completion).
...
.
Value
A '>goGARCHforecast object containing details of the GO-GARCH
forecast.