https://en.wikipedia.org/wiki/K-medoids
https://stats.stackexchange.com/questions/51743/how-is-finding-the-centroid-different-from-finding-the-mean
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5148156/#S2title
https://piazza.com/class_profile/get_resource/j77vxubgf91p3/j8dcnh2y8a53hj
https://piazza.com/class_profile/get_resource/j77vxubgf91p3/j85bv944u6p5vs