power.anova.test <-
function (groups = NULL, n = NULL, between.var = NULL, within.var = NULL,
	  sig.level = 0.05, power = NULL)
{
    ## Check parameters
    if (sum(sapply(list(groups, n, between.var, within.var, power, sig.level),
		   is.null)) != 1)
	stop("exactly one of 'groups', 'n', 'between.var', 'within.var', 'power', and 'sig.level' must be NULL")
    if (!is.null(groups) && groups < 2)
      stop("number of groups must be at least 2")
    if (!is.null(n) && n < 2)
      stop("number of observations in each group must be at least 2")
    if(!is.null(sig.level) && !is.numeric(sig.level) ||
       any(0 > sig.level | sig.level > 1))
	stop("'sig.level' must be numeric in [0, 1]")

    p.body <- quote({
	lambda <- (groups-1)*n*(between.var/within.var)
	pf(qf(sig.level, groups-1, (n-1)*groups, lower = FALSE),
	   groups-1, (n-1)*groups, lambda, lower = FALSE)
    })

    if (is.null(power))
	power <- eval(p.body)
    else if (is.null(groups))
	groups <- uniroot(function(groups) eval(p.body) - power,
			  c(2, 1e+02))$root
    else if (is.null(n))
	n <- uniroot(function(n) eval(p.body) - power, c(2, 1e+05))$root
    else if (is.null(within.var))
	within.var <- uniroot(function(within.var) eval(p.body) - power,
			      between.var * c(1e-07, 1e+07))$root
    else if (is.null(between.var))
	between.var <- uniroot(function(between.var) eval(p.body) - power,
			       within.var * c(1e-07, 1e+07))$root
    else if (is.null(sig.level))
	sig.level <- uniroot(function(sig.level) eval(p.body) - power,
			     c(1e-10, 1 - 1e-10))$root
    else stop("internal error")
    NOTE <- "n is number in each group"
    METHOD <- "Balanced one-way analysis of variance power calculation"
    structure(list(groups = groups, n = n, between.var = between.var,
		   within.var = within.var, sig.level = sig.level,
		   power = power, note = NOTE, method = METHOD),
	      class = "power.htest")
}