For each pair of characteristic vectors, Ti and Tj, the correlation coefficient can be written as: Cij=∑k=1m[Ti(k)−⟨Ti⟩]•[Tj(k)−⟨Tj⟩]∑k=1m[Ti(k)−⟨Ti⟩]2•∑k=1m[Tj(k)−⟨Tj⟩]2(1) M is the dimension of the characteristic vector and ⟨Tj⟩=∑k=1mTj(k)/M, ⟨Ti⟩=∑k=1mTi(k)/M.