The following example performs hierarchical clustering on the rlog transformed expression matrix subsetted by the DEGs identified in the above differential expression analysis. It uses a Pearson correlation-based distance measure and complete linkage for cluster joining.

geneids <- unique(as.character(unlist(DEG_list[[1]])))
y <- assay(rlog(dds))[geneids, ]
pheatmap(y, scale="row", clustering_distance_rows="correlation", clustering_distance_cols="correlation")

Figure 6: Heat Map with Hierarchical Clustering Dendrograms of DEGs