what is the phi model parameter which model is a phi matrix? why does phi_k measure autocorrelation what are the parameters of a var model why do we use the phi matrix in a model? var phi model parameters what is the definition of phi matrix what is phi_epsilon_t phi equation definition var coefficient what is phi coefficient what is the phi coefficient what is phi-matrix correlation which model is dependent on the phi model? what is the purpose of the coefficients of a var (p) model? what is the coefficient of a variance model what are phi coefficients what is the coefficient in var what is the definition of the coefficients in a par model what is the coefficient for a var model