Fig. 2

A multidimensional scaling (MDS) plot of the merged gene expression data.a This panel shows that without removal of the batch effect, all samples are clustered by experiment and by platform (not by the biological variable of interest) inside the MDS space. b With intra-platform batch adjustment, the samples are intermingled on the basis of the biological variable. All samples are color coded by biological variables (normal: red, cancer: green), with different symbols corresponding to different studies