\[P_X\ =\ P2-P1\]
The distance or number of samples between the maximum peak value (P1) of the EOG signal and the minimum peak value (P2) was the final predictor (Px )chosen to classify the vertical movement of the EOG signal. The distance between peaks is simply calculated by subtracting P1 from P2. Figure 10.4 illustrates this process for and blink movement of the EOG signal.