Fig. 7From: Time-trend analysis of the center frequency of the intrinsic mode function from the Hilbert–Huang transform of electroencephalography during general anesthesia: a retrospective observational studyThe quality of curve fitting for 10 individual patients. The regression line was obtained from the Gaussian process regression shown in Fig. 6. Each panel shows a scatter plot showing the relationship between BIS and HHT_IF in an individual patient. Root mean square error (RMSE) and coefficient of determination (R2) are shown in the upper left cornersBack to article page