Average linkage hierarchical clustering example. The expression of 44 genes was measured in 4 experiments (E1, E2, E3, E4). The genes were classified according to their coexpression levels. The Pearson Correlation Coefficient was used (r- value) to analyze gene set signal values. Genes were clustered according to the r- value correlation matrix using the Average Linkage Hierarchical clustering method. The tree on the left clusters the expressions of the genes whereas the tree on top of the figure clusters the profiles of the experiments. Thus experiments E2 and E3 are similar and closely related.