Overview of asteroid spectra assigned to each cluster, including the number N of spectra and the asteroid classes to which the cluster contributes, excluding classes with fewer than three contributed observations except for cluster 25 which only has three members. The classes are sorted by the total number of observations the cluster contributed. The dotted line gives the mean value of the spectra per cluster except for diffuse clusters (defined in Sect. 3.3) and cluster 25. The mean spectra are normalised to unity at 0.55 urn. The y-axis limits change in each row.