1. File list:
step-acc.mat
    Include five variables:
        x: raw acceleration in x dimention
        y: raw acceleration in y dimention
        z: raw acceleration in z dimention
        timestamp: raw timestamps in miliseconds
        step_event: binary series, 0: no step, 1: step occurred.

2. The acceleration are raw, it contains gravity. All the data are collected with attitude (heading=y axis, face-up).

3. The dataset has 100 steps.