Fig. 3

Decision tree analysis for discrimination between Groups I + II and Groups III + IV. The node (the frame) shows the group (I + II, III + IV), the number of cases, as well as the proportion of the total data. If the element (split condition expression) is satisfied, it goes left (node); if not, to the right. The color of the node indicates “I + II > III + IV” for blue and “III + IV > I + II” for green. The darker the node’s color, the lower its entropy (average information content); that is, the higher its purity. For example, if a node is dark green, it indicates that the node is mostly III + IV, indicating high classification accuracy. Note that the one order of magnitude for SII is smaller than that of the original. Group I: cellulitis; Group II: cellulitis with shallow abscess formation; Group III: deep neck abscess; and Group IV: necrotizing soft tissue infection. CRP C-reactive protein, NLR neutrophil-to-lymphocyte ratio, PLR platelet-to-lymphocyte ratio; SII, systemic immune-inflammation index