esttransfer2 <- function(x,y) {
f <- spectrum(ts.union(x,y),spans=c(3,3))
A <- (f$spec[,1])/(f$spec[,2])
A <- sqrt(A)
A <- A*exp(1i*f$phase)
n <- length(A)
tl <- seq((n-1):2)
A <- c(A, Conj(A[tl]))
varA <- ((f$coh)^{-2}-1)/(2*(f$df-1))
par(mfrow=c(2,1))
plot(f$freq, log(Mod(A[1:length(f$freq)])), type="l", main="Estimate of log of Mod Transfer fcn")
lines(f$freq, log(Mod(A[1:length(f$freq)]))+2*sqrt(varA), lty=2)
lines(f$freq, log(Mod(A[1:length(f$freq)]))-2*sqrt(varA), lty=2)
plot(f$freq, f$phase, type="l", main="Estimate of Arg of Transfer fcn")
lines(f$freq, f$phase+2*sqrt(varA), lty=2)
lines(f$freq,f$phase -2*sqrt(varA), lty=2)
}