"garch11v" <- function(rt,mu,a0,a1,b1){
# Computes volatility series for GARCH(1,1) models.
# rt: return series
# mu: mean of rt
# a0: alpha_0
# a1: alpha_1
# b1: beta_1
T=length(rt)
at=rt-mu
sigtsq=rep(0,T)
z0=mean(at^2)
sigtsq[1]= a0 + a1*z0 + b1*z0
atsq=at^2
for (i in 2:T){
ii=i-1
sigtsq[i]=a0+a1*atsq[ii]+b1*sigtsq[ii]
}
garch11v <- list(condvars=sigtsq,atsq=atsq)
}