PMC5319343_01
A demonstration of adding small oscillations in EMD computation to eliminate spurious large values in IMFs. (a) A 5 s segment of data with about 0.4 s zeros, as indicated by the dotted circle. (b-f) The first 5 IMFs directly calculated from the data in (a). (g) Data (a) with added small oscillations on the scale of unity (see text), which is almost invisible from the figure. (h-l) The first 5 IMFs calculated from the data in (g). Insets of (g) and (k) show magnification of the zero region. Note that the scale of the y axis is much larger in (b-f) than those in (h-l). The anomalies appeared in (b-f) are effectively removed by the simple method of adding small oscillations to the data segment.
rsos160741-g11.jpg
PMC5319343_01_rsos160741-g11.jpg
RSOS160741F11
In such a case, the EMD program may diverge or have abnormally large values (figure 11a-f). IMFs will contain the added small sinusoidal oscillations instead of generating divergence or large anomalies (figure 11g-l). In addition, when the original data is contaminated by a small segment of zeros, without adding the small oscillations, the resulting IMFs will oscillate wildly in this region with amplitudes orders of magnitude larger than those of the normal datasets (figure 11a-f).