Figure 1

Classification of lung cancer vs . normal samples by the decision tree algorithm. The left branch node after the first layer is the cases of peak intensity under 2.018, the right one is over or equal to 2.018. The cutoff points for 8245, 6429 and 2538 Da were 1.574, 49.64 and 13.01, respectively. The cutoff points of mass 5335 Da were 0.288 (left) and 2.163 (right). N represents the number of samples. M represents the molecular weight.