Chapter 3 Page Rank Vector Flashcards
Explain two methods of page ranking
- More pointers to a webpage from other pages the more important it should be
- Webpages are important if they are pointed to by many important webpages. aka pointers come from pages that are more important.
What is page rank
Ranking of pages on Google
What does Pi points to Pj mean
Means Pi contains a reference address of webpage Pj
What is |Pj|
Number of pages Pj points to. For simiplicty its assumed to be greater than 0
Explain in words the inital step of defining the page rank vector
We define all webpages to be equally important so the zeroth iterate of the page rank vector will be (1/m , 1/m, 1/m ….) for all m where Pi are the pages up to Pm
Explain in words the second step of defining the page rank vector - first iterate
We define the page rank vector first iterate to be :
r1 n= (r1(P1), ….. ,r1(Pm)) r1(Pi) will be the previous iterate for any page that pointed to pi page so r0(Pj) divided by |Pj| summed over all j
What is the sum of the terms in the page rank vector
1
How do we find the true page rank vector
Find the limit of rk
How can we interpret the page rank vector
The bigger the element in the vector the more important the page. So if vector is (x1,…. xn) the bigger xi the more important page i is.
Explain a diagraph
Diagraph associated with a web is a directed graph with vertices P1,….PN corresponding the the webpages and there is an edge i—>j if Pi points to Pj
What is the adjacency matrix
A = (Aij) is the adjacency matrix of diagraph with m vertices so is m x m 0 and 1 matrix with aij = 1 if Pi points to Pj and Aij =0 is Pi does not point to Pj
What does row denote in adjacency matrix
Row i denotes what pages Pi points to
What does column denote in adjacency matrix
Column j denotes what is pointing to Pj
Define the H matrix of a web with adjacency matrix A m x m
m x m matrix obtained from A by dividing the entries in row i of A by the number of ones in row i
