Figure 3
From: Calculate excess mortality during heatwaves using Hilbert-Huang transform algorithm
Significance test to separate trend IMFs from non-trend IMFs and standard autocorrelation function (ACF) plot. The solid line without circle points (middle-left plot) is the fractional white noise energy level line. The dashed lines in the ACF plots (bottom row) are the approximate 95% confidence bands. Dotted line is the approximate 95% confidence band (upper limit); dashed line is the 99% confidence band (upper limit).