Average value of variables in groups obtained with ONC-T data analysis. Values are the following: panel a: average spectra normalized to reflectance at 548.9 nm correspond to the two groups obtained with a 3σ confidence level; and panel b: average spectra normalized to reflectance at 548.9 nm correspond to the six groups obtained with a 2σ confidence level. The error bar corresponds to the standard deviation of the distribution of the objects in each group.