Stars identified in the test sample. Panel a: color locus occupied by the stars (black points) compared to the color locus occupied by the non-stars, i.e. galaxies and AGN (gray points) adopting a probability threshold of 50%. Panel b: completeness (gray dot-dashed line) and purity (black solid line) of the identified star sample for each given probability threshold given on the x-axis. Panel c: summary of the performance of the classifier in a confusion matrix.