Mean mean1, mean2, combined;
foreach(i; 0..5) {
    mean1.put(i);
}

foreach(i; 5..10) {
    mean2.put(i);
}

mean1.put(mean2);

foreach(i; 0..10) {
    combined.put(i);
}

assert(approxEqual(combined.mean, mean1.mean));