Fig. 7
The results of interaction factor analysis for MCH distribution. NE nonlinear enhancement, BE bi-factor enhancement. X1: Proportion of mountainous area; X2: Land area; X3: Altitude; X4: River density; X5: Annual average temperature; X6: Annual precipitation; X7: Annual sunshine duration; X8: Ethnic minority population; X9: Proportion of ethnic minority population; X10: Proportion of urban population; X11: Per capita GDP; X12: GDP of Agriculture; X13: GDP of Industrial; X14: GDP of Service; X15: Railway mileage; X16: Road mileage; X17: Historical settlement