what is the model gach which variable is an exogenous variable in r how to add exogenous variable in garch is x a variable if a variable is exogenous can i put it in a fit and compare the two models? which r variable is the exogeneous model what variables can be used to create a fit model why are variables exogenous and os calculating exogenous variables in r what is a exogenous variable in garch what variables is an example of an exogenous curve how to add exogeneous variables to a hatch model which variables are exogeneous how to insert exogeneous variables in garch model what is a exogenous variable in r how to add exogeneous variables to a r curve in r r how to add exogenous variables to garch model is $x$ a r variable what is the purpose of the model in r how do I do a fit on $y$?