中文说明：这种方法计算利用中心差分法对信号的导数。这种方法的优点是它并没有降低中处理信号即长度信号仍然相同的样本数。
English Description：
This method calculates derivative of the signal using central difference method. The advantage of this method is that it did not decrease number of samples in processing signal i.e. the length of the signal remains the same.