Page Rank 算法及其 Python 实现
pythonprogrammingserver side programming
PageRank 算法适用于网页。网页是一个有向图，我们知道有向图的两个组成部分是节点和连接。页面是节点，超链接是连接，即两个节点之间的连接。
我们可以通过 PageRank 找出每个页面的重要性，而且它是准确的。PageRank 的值是介于 0 和 1 之间的概率。
图中单个节点的 PageRank 值取决于与其连接的所有节点的 PageRank 值，这些节点循环连接到我们想要排名的节点，我们使用收敛迭代方法为 PageRank 分配值。
示例代码
import numpy as np
import scipy as sc
import pandas as pd
from fractions import Fraction
def display_format(my_vector, my_decimal):
return np.round((my_vector).astype(np.float), decimals=my_decimal)
my_dp = Fraction(1,3)
Mat = np.matrix([[0,0,1],
[Fraction(1,2),0,0],
[Fraction(1,2),1,0]])
Ex = np.zeros((3,3))
Ex[:] = my_dp
beta = 0.7
Al = beta * Mat + ((1-beta) * Ex)
r = np.matrix([my_dp, my_dp, my_dp])
r = np.transpose(r)
previous_r = r
for i in range(1,100):
r = Al * r
print (display_format(r,3))
if (previous_r==r).all():
break
previous_r = r
print ("Final:\n", display_format(r,3))
print ("sum", np.sum(r))
输出
[[0.333] [0.217] [0.45 ]] [[0.415] [0.217] [0.368]] [[0.358] [0.245] [0.397]] [[0.378] [0.225] [0.397]] [[0.378] [0.232] [0.39 ]] [[0.373] [0.232] [0.395]] [[0.376] [0.231] [0.393]] [[0.375] [0.232] [0.393]] [[0.375] [0.231] [0.394]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] [[0.375] [0.231] [0.393]] Final: [[0.375] [0.231] [0.393]] sum 0.9999999999999951
