Figure . The split region of the normal and the anomalous data of the 4-HAP network identified by the isolation forest algorithm. Red triangles are data assigned to the normal region and blue circles resemble data not grouped with the majority. The isolation forest was performed with a contamination rate of (a) 1.5×10 -3 , (b) 5×10 -4 , (c) 9.5×10 -4 , (d) 1×10 -3 .