Figure 2

Overview of subgroup-specific gene-centering algorithm. (a) Distribution of gene expression for a representative gene from the entire University of North Carolina (UNC) training cohort, with the global mean represented by the gray vertical dotted line. (b) The gene expression baseline is approximated by the global mean (gray dotted line) shown on the global distribution, represented as a mixture of estrogen receptor (ER)-positive cases (shown in pink) and ER-negative cases (shown in green). (c) and (d) The global median is located on different percentiles for the ER-positive and ER-negative cases, and each differs with respect to each subgroup mean. (e) The distribution of gene expression for the same gene in a study cohort composed of only ER-positive cases. The baseline value for subgroup-specific gene centering is estimated at the corresponding percentile of the ER-positive subgroup in the study cohort and compared with the median value, represented by the red vertical dotted line. The difference between these values is the error introduced by standard gene centering. (f) Similar to (e), but for the ER-negative subgroup.