PageRank Calculation
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| What is PageRank? |
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PageRank, named after Larry Page (an American computer scientist and internet entrepreneur who, with Sergey Brin, is best known as the co-founder of Google),
is an algorithm used by Google Internet Search Engine to analyze websites' ranks and links. The algorithm is applied to any collection of sites with hyperlink references.
A hyperlink reference to a web page is counted as a "vote." The PageRank of a page depends on all pages that link to it. A web page that is linked by many pages with high PageRank
value receives a high rank itself.
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| How to use the algorithm to calculate PageRank? |
| A simplified PageRank calculation uses a probability distribution to represent a random clicking on links. A probability uses a numeric value between 0 and 1.
A 0.5 probability is commomly said as a "50% chance." Therefore, a PageRank of 0.5 from the PageRank calculation means there is 50% chance that a random link goes to the page which has 0.5 PageRank value.
To illustrate how to perform the value of PageRank calculation, we assume there are four web pages: A, B, C, and D. The initial value of each page is 0.25, because we assume the initial PR value of the entire network of 4 sites is 1,
and each of them evenly distributed as shown in Figure 1.
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If Pages B, C, and D each only link to A, Page A would have 0.75 because it gets 0.25 from B, C, and D (Figure 2).
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If Pages B has a link to page C and page A, while Page D has links to all other pages (Figure 3). The value of the PageRank will be divided among all the outbound links on a page.
Therefore, Page A would be 0.458 (0.125 + 0.083 + 0.25), page B would be 0.083, page C would be 0.125+0.083, and page D is 0.
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In general, the Pagerank value of a page is equal to the sum of the PageRank values of the distributed pages divided by the numbers of their outbound links.
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| How many links do I need to achieve a certain PageRank value? |
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There is a PageRank Calculation chart to show you appoximately how many links to achieve a certain PR in a "perfect condition." For example, if you want to your page to be PR5,
you will need 16,803 PR1, 3,055 PR2, 555 PR3, 101 PR4, 19 PR5, 4 PR6, 1 PR7, 1 PR8, 1 PR9, or 1 PR10 sites to link to your page. Please note, the PageRank calculation is based on the "perfect condition" of
the outbound linking sites. The "perfect condition" of PageRank calculation means each PR1 to PR10 site has less than 3 outbound links. In reality, it is impossible. Therefore, you will need more high PageRank links than
the numbers shown in the PagRank Calculation chart.
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Pagerank Calculation |
| PR Value |
Links for PR3 |
Links for PR4 |
Links for PR5 |
Links for PR6 |
Links for PR7 |
Links for PR8 |
| PR1 |
555 |
3,055 |
16,803 |
92,414 |
508,277 |
2,795,522 |
| PR2 |
101 |
555 |
3,055 |
16,803 |
92,414 |
508,277 |
| PR3 |
19 |
101 |
555 |
3,055 |
16,803 |
92,414 |
| PR4 |
4 |
19 |
101 |
555 |
3,055 |
16,803 |
| PR5 |
1 |
4 |
19 |
101 |
555 |
3,055 |
| PR6 |
1 |
1 |
4 |
19 |
101 |
555 |
| PR7 |
1 |
1 |
1 |
4 |
19 |
101 |
| PR8 |
1 |
1 |
1 |
1 |
4 |
19 |
| PR9 |
1 |
1 |
1 |
1 |
1 |
4 |
| PR10 |
1 |
1 |
1 |
1 |
1 |
1 |
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