TRPC6 and chronic obstructive pulmonary disease: Figure 4 shows that all three decision tree models optimized for the classification of COPD contained only one TRPC6 gene (7225_at). The result is unusual because machine learning results using a conventional microarray or RNA-sequencing generally do not determine disease classification using only one gene. Figure 6 and Figure 7 show the results of the same experiment but with the GSE57148 [30] data, and revealed that the results with the J48 classifier came in a complex tree form while at the same time performing poorly overall.