[Gretl-users] The constant in the mean equation of ARCH/GARCH

Dear all, I am using gretl 1.6.6 now. It seems that the constant term in the mean equation of ARCH/GARCH estimation is automatically added though the default function by click \Model\Time series\ARCH or GARCH looks that the const as a independant variable can be removed. Is it required to have a constant term in the mean equation of ARCH/GARCH? Is it possible to remove the constant term in the mean equation with ARCH/GARCH estimation? Thanks Yi-Nung Yang Chung Yuan Christian University, Taiwan