Clustering of star abundances. Left panel: [Eu/Fe] ratios as in Fig. 2 (left panel), but divided into three k-means clusters, coinciding with increasing correlation strengths in Table 4 and the appearance of spurious correlations. Right panel: if we choose to divide into seven clusters, intermediate transition clusters appear in the interval −2.5 < [Fe/H] < −1, where an increasingly higher number of different r-process events tends to result in a change to an average [Eu/Fe] value, before around the kink at [Fe/H] = −1 the domination of core-collapse supernovae turns over to a type Ia supernova domination. For [Fe/H] < −2.5 we see the division in limited-r, r-I, and r-II stars, showing that they indicate different abundance behaviors.