Cross-validation (CV) results for Crohn’s disease study: most frequent taxa and most frequent balances selected in the CV procedure compared to the global balance obtained with the whole data set. Cross-validation (CV) results for Crohn’s disease study: most frequent taxa and most frequent balances selected in the CV procedure compared to the global balance obtained with the whole data set. Colored rectangles indicate if the component is in the numerator of the balance (BAL) (red), in the denominator (blue), or not included (white). FREQ, frequency. J. Rivera-Pinto et al. mSystems 2018; doi:10.1128/mSystems.00053-18