【皮尔逊相关系数】类似于余弦定理的使用(推荐),直接上代码

# 也是用于内容推荐


def pearson(p, q):
    # 只计算两者共同有的
    same = 0
    for i in p:
        if i in q:
            same += 1

    n = same
    # 分别求p，q的和
    sumx = sum([p[i] for i in range(n)])
    sumy = sum([q[i] for i in range(n)])
    # 分别求出p，q的平方和
    sumxsq = sum([p[i] ** 2 for i in range(n)])
    sumysq = sum([q[i] ** 2 for i in range(n)])
    # 求出p，q的乘积和
    sumxy = sum([p[i] * q[i] for i in range(n)])
    # print sumxy
    # 求出pearson相关系数
    up = sumxy - sumx * sumy / n
    down = ((sumxsq - pow(sumxsq, 2) / n) * (sumysq - pow(sumysq, 2) / n)) ** .5
    # 若down为零则不能计算，return 0
    if down == 0: return 0
    r = up / down
    return r



p = [0,1,1,1]
q = [0,1,1,1]
print (pearson(p,q))

# 得出的结果是1.0

 

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