I'm evaluating the impact of two variables on stock returns. For this I am using a Garch(1,1)-model in RStudio. This is the result I am getting. Why is the garch model not a valid choice? The external regressors are in the variace model, because they are not incorporated in the mean equation.
> myspec<-ugarchspec(variance.model=list(model="sGarch", garchOrder=c(1,1),external.regressors=mydata), + mean.model=list(armaOrder=c(1,0),include.mean=TRUE)) Error: ugarchspec-->error: the garch model does not appear to be a valid choice.