Fig 1. Results for selecting optimal cluster size using the elbow method (Panel A), silhouette method (Panel B) and the gap_statistic method (Panel C).

Selection for the elbow method is based on the largest local derivative of the within groups sum of squares (Panel A triangles), the maximum silhouette width (Panel B) and the first non-negative value for Gap(k)-(Gap(k + 1)−sd_k+1) (Panel C triangles). These results indicate an optimal number of clusters in the 26–28 range. Panel D displays the GI50_codebook dendrogram (Euclidean, Ward’s) with cuts at 28 (red lines) and 7 clusters (green lines), respectively.