Fig. 3

Comparison of log₂ ratios derived from relative abundances and after applying SCML to all background OTUs. Observed log₂ ratio versus expected log₂ ratio of all background OTUs for all pairwise comparisons as derived from (a) relative abundances and (b) SCML by S. ruber. The data is binned to hexagons because of the high number of data points. The colour of each hexagon represents the percentage of counts at the corresponding level of expected log₂ ratios contained in each bin. Bins that contributed to <0.05 % for each level of expected log₂ ratio are omitted. The purple diagonal represents the identity, which represents the expected log₂ ratios by design. The box-plots in (c) show the error between the expected and observed log₂ ratios for both approaches. The smaller this error, the better calibrated the ratios are