Scatter plot of MDS variables c₁ vs. c₂ (a, b) and c₁ vs. c₃ (c, d) where is the projection of the similarity matrix onto the ith eigenvector of the normalized Laplacian of the similarity matrix when using the NMF coefficients. Each point corresponds to one AR and they are labeled according to the clustering (a, c) and the Mount Wilson labels (b, d). In this space, the clusters data appear to be separable and there are concentrations of complex ARs in the region with lowest c₁ values. Other patterns are described in the text.