iOS - High pass filter equation for accelerometer

Question

Could someone explain how one arrives at the equation below for high pass filtering of the accelerometer values? I don\'t need mathematical derivation, just an intuitive interpr

Answer 1

Okay, what that code is doing is calculating a low-pass signal and then substracting the current value.

Thing of a square wave that takes two values 5 and 10. In other words, it oscillates between 5 and 10. Then the low pass signal is trying to find the mean (7.5). The high-pass signal is then calculated as current value minus mean, i.e. 10 - 7.5 = 2.5, or 5 - 7.5 = -2.5.

The low-pass signal is computed by integrating over past values by adding a fraction of the current value to 90% of the past low-pass value.