说明：  基于PAA的分段线性表示算法:用等宽度窗口分割时间序列，每个窗口内的时间序列用窗口平均值来表示，就得到了时间序列的一种分段线性表示，它的输入参数为分段数，记为K.
(PAA-based algorithm for piecewise linear representation: split time series with windows of same width , use the mean of time series in the window to express, it has been a sub-linear time series that it s input parameters as the number of sections, denoted by K.)