However, there were also some structures which showed low model accuracy (error > 3 kcal/mol, 12.552 kJ/mol), likely due to the type of descriptors utilized to make predictions and absence of sufficient structure representations in the training data. When analyzing these structures with poor model accuracy, R2sub-I (error of 13.8 kcal/mol, 57.7 kJ/mol), R2sub-II (error of 8.0 kcal/mol, 33.5 kJ/mol), and R2sub-IV (error of 10.2 kcal/mol, 42.6 kJ/mol), we found that each NCB had at least three descriptors used in the model which were outside the range seen by the initial library.