Data before analysis in the following figure are time series data changing over time. Power Spectrum analysis is applied when transforming such time series signals into frequency domain signals. Select data you want to apply this method in Analysis Window and click the icon of Power Spectrum Estimation by FFT in Analysis Tool Bar. Then, time series data by channels are transformed into frequency domain data and they are shown as 2-D graph in Display Window, which is registered at Analysis Window.
The x-axis represents time before analysis, but, in the graph showing Power Spectrum analysis, the x-axis represents frequency and the y-axis represents power value for each frequency value. Accordingly, this Power Spectrum graph reveals how many frequency components are included in time series signals. Further, circular graphs shown in the right side reveal the percentage of each frequency band.