皮爾遜積矩相關系數,又稱“相關系數”，
取值范圍為[-1,1]，r=0，沒有相關性。
-1：表示方向完全相反
1：表示方向相同，並且完全一樣
0：表示沒有相關性
函數簽名：
numpy.corrcoef(x, y=None, rowvar=True, bias=<no value>, ddof=<no value>)
rowvar：True，表示每行代表一個變量，列中包含觀測值。否則，關系將被轉置：每列表示一個變量，而行包含觀測值。
參考：
https://www.osgeo.cn/numpy/reference/generated/numpy.corrcoef.html # 中文說明文檔
https://numpy.org/doc/stable/reference/generated/numpy.corrcoef.html # 英文說明文檔
內容如下：
numpy.corrcoef numpy.corrcoef(x, y=None, rowvar=True, bias=<no value>, ddof=<no value>)[source] Return Pearson product-moment correlation coefficients. Please refer to the documentation for cov for more detail. The relationship between the correlation coefficient matrix, R, and the covariance matrix, C, is R_{ij} = { C_{ij} } / { sqrt{ C_{ii} * C_{jj} } } Parameters xarray_like A 1-D or 2-D array containing multiple variables and observations. Each row of x represents a variable, and each column a single observation of all those variables. Also see rowvar below. yarray_like, optional An additional set of variables and observations. y has the same shape as x. rowvarbool, optional If rowvar is True (default), then each row represents a variable, with observations in the columns. Otherwise, the relationship is transposed: each column represents a variable, while the rows contain observations. bias_NoValue, optional Has no effect, do not use. Deprecated since version 1.10.0. ddof_NoValue, optional Has no effect, do not use. Deprecated since version 1.10.0. Returns Rndarray The correlation coefficient matrix of the variables.