Figure compares the deviations of the XGB, FNN and XGB-FNN models on the DGLOO test sets with either the similarity or the activation energy as a descriptor. The activation energy-based results are taken from our previous work. The boxplot consists of the most extreme values in the data set (the green lines), the lower and upper quartiles (the black box), the median (the red line), the mean (the blue dashed line) and potential outliers (discrete red dots). The top three panels show the deviations with the similarity as the descriptor while the bottom three panels refer to previous results from the activation energy. Note that the reactions involving the reactant CH4 are excluded from the LOO test dataset since the similarity between the reactant CH4 and the product CH3 is 0. For the reactions between alkanes and CH3 (the first column), the deviations with the similarity as a descriptor are mostly distributed in between 75% and 225% for the three models, slightly smaller than those obtained using the activation energy as a descriptor, which are largely located in between 75% and 300%. For the reactions between alkanes and H (the middle column), the deviations with the similarity as a descriptor are mainly distributed in between 75% (75%, 75%) and 150% (225%, 200%)