Fourteen-cluster classification of the noiseless spectra. Top left: number of spectra contained in each class. All others: heatmaps of the relevant CIGALE input parameters among the 14 classes on noiseless spectra. All possible parameter values (see Table A.1) are represented on the y-axis, and the class index on the x-axis. The within-class densities of the parameter values are illustrated in the form of a heatmap, where a dark square equates to a density of 1, and white of 0. The classes are sorted by ascending average T_main.