Prediction of test set classification by correlation to exemplar HPI and LPI transcriptional profiles. The same exemplar samples were used for HPI (x-axis) and LPI (y-axis) as in Figure. 3, and quadrants were similarly defined. PCC values of test set samples to each exemplar were plotted, and LPI and HPI samples located in quadrants II and IV, respectively, were considered accurately classified. (A) Using all genes in the compendium. (B) Using Fisher's statistic-derived digital signature genes. (C) Using z-test-derived analog signature genes.