Google PageRank - item 4

PageRank is the algorithm used by Google's search engine.  It is based on the theory that the importance of a research paper can be judged and rated by the number of citations the paper has from other research papers.

The inventors of the algorithm  Sergey Brin and Larry Page, transferred the research paper importance theory to the web, making so each web page can be judged by the number of hyperlinks which are pointing to it from other web pages. (Horrell M., 2001)

Example of the theory behind PageRank.

What is this equation?

PR(A) = (1 - d) + d(PR(t1)/C(t1) + ... + PR(tn)/C(tn))

Legend:

• 'PR(A)' is the web page's PageRank
• 't1' & 'tn' are pages which link to page A
• 'C' number of outbound links the page has
• 'd' the damping factor (usually set at 0.85)

How does it work?

A simpler version to understand is:

a page's PageRank = 0.15 + 0.85 * (linking page's PageRank/number of outbound links on page)

In plain terms, a page's PageRank is calculated by dividing a page's number of inbound links with its number of outbound links (inbound/outbound). Then the value is multiplied by the damping factor. Finally the product of "1 minus the damping factor" is then added to the result. The final product is then achieved.

References
Horrell M.(2001), The Google PageRank Algorithm. Retrieved from http://www.markhorrell.com/seo/pagerank.html