Matrices of size: n.observations x n.samples
mu.obs.samples <- extract(fit, sample = "train")
mu.cf.samples <- extract(fit, sample = "test")
z <- data$z
mu.1.samples <- z * mu.obs.samples + (1 - z) * mu.cf.samples
mu.0.samples <- (1 - z) * mu.obs.samples+z* mu.cf.samples
icate.samples <- mu.1.samples - mu.0.samples
cate.samples <- rowMeans(icate.samples)