Improvements of fuzzy C-means clustering performance using particle swarm optimization on student grouping based on learning activity in a digital learning media. - Ahmad Afif Supianto; Nur Sa'diyah; Candra Dewi; Retno Indah Rokhmawati; Satrio Agung Wicaksono; Hanifah Muslimah Az-zahra; Satrio Hadi Wijoyo; Yusuke Hayashi; Tsukasa Hirashima (SIET, 2020)