## transform eq. 1 ##
t1 = function (lambda, y) {
  1/lambda * log(y^lambda / (1-y^lambda))
}

pow1.lambda = function (lambda, y) {
  n = length(y)
  y.lambda = t1(lambda, y)
  yl.bar = mean(y.lambda)
  sigmasq = mean((y.lambda - yl.bar)^2)
  -n/2 * log(sigmasq) - n/2 + (lambda-1)*sum(log(y))
}