Fig. 1

Distribution of DNA methylation between ER/PR-negative and ER/PR-positive samples in the training dataset (BCCC). a Box plot of mean β values. The level of methylation at each CpG site was defined by β values. β values close to 0 indicated low level of DNA methylation, and β values close to 1 indicated high level of DNA methylation. The next levels of analysis were conducted at the gene level. Mean β values were averaged for all CpG sites on the array for each individual gene. Statistical significance of difference in β values for each gene between the two groups was determined by ks and Wilcox tests. b Scatter plot analysis of mean β values