Fig. 1

a A heatmap of ranking values for the top 30 single miRNA references identified by averaging ranking across datasets. The miRNA shown have the lowest ranking value averaged from all datasets. Color intensity represents the ranking value in a dataset, averaged from the four stability measurement algorithms. The lower the stability value, the better the reference miRNA. MiRNAs at the top were considered the best single normalizers. MiRNAs with missing expression values in more than 20% of datasets were filtered out. Values were not standardized. b A heatmap of average raw expression values of miRNAs in each dataset. It suggests that raw expression values of top reference single miRNAs are heterogeneous, thus implying that a combination of them might be a good reference. Expression values were not standardized