Cumulative distributions of the absolute fractional flux error in the red part of the spectra in the training set: (i) when the weights used to reconstruct the spectrum are those obtained from the red part of the spectrum (method 1, grey line); (ii) when the projection matrix is used (method 2, black lines). Median values are displayed (dashed vertical lines) together with 90th percentiles (dot-dot-dashed vertical lines).