ask = function(){
    eval(parse(prompt = paste("   Enter confidence coefficent", ": ", sep="")))
}
conf.bands <- function(surv.object, conf.type='plain', type='ep', tL=NA, tU=NA){
	s <- surv.object
	fit <- survfit(s ~ 1)
	n <- length(s)/2
	time <- summary(fit)$time
	std.err <- summary(fit)$std.err
	surv <- summary(fit)$surv
	if(is.na(tL)){
		t.L <- time[1]
	} else {
		temp <- time[time <= tL]
		t.L <- temp[length(temp)]
	}
	if(is.na(tU)){
		t.U <- time[length(time)]
	} else {
		temp <- time[time <= tU]
		t.U <- temp[length(temp)]
	}
	t.L.pos <- which(time == t.L)
	t.U.pos <- which(time == t.U)
	sigma.2 <- ( std.err / surv )^2
	a.L <- n*sigma.2[time == t.L]/(1+n*sigma.2[time == t.L])
	a.U <- n*sigma.2[time == t.U]/(1+n*sigma.2[time == t.U])
	cat("   a_L: ",a.L,"   |   a_U: ", a.U, "\n", sep="")
	input <- ask()
	if(type == 'hall'){
		m.fact <- input*(1+n*sigma.2)/sqrt(n)
	} else {
		m.fact <- input*sqrt(sigma.2)
	}
	CI <- matrix(NA, length(surv), 2)
	if(conf.type == 'log-log'){
		theta <- exp(m.fact/log(surv))
		CI[,1] <- (surv)^(1/theta)
		CI[,2] <- (surv)^(theta)
	} else if(conf.type == 'asin-sqrt'){
		temp <- asin(sqrt(surv)) - 0.5*m.fact*sqrt(surv/(1-surv))
		lower <- apply(cbind(rep(0, length(temp)), temp), 1, max)
		CI[,1] <- (sin(lower))^2
		temp <- asin(sqrt(surv)) + 0.5*m.fact*sqrt(surv/(1-surv))
		upper <- apply(cbind(rep(pi/2, length(temp)), temp), 1, min)
		CI[,2] <- (sin(upper))^2
	} else {
		CI[,1] <- surv*(1-m.fact)
		CI[,2] <- surv*(1+m.fact)
	}
	CI[CI[,1] < 0, 1] <- 0
	CI[CI[,2] > 1, 2] <- 1
	list(time=time, lower=CI[,1], upper=CI[,2])
}