Page Rank Computation
In this section, I will show you how to use the page rank formula to compute page rank of each web page using MS Excel iteration. Spreadsheet companion of this tutorial can be downloaded here.
To implement our numerical example above, we have a small network of 6 nodes with
link matrix
as follow:
To compute page rank using spreadsheet, we first compute the term
from the link matrix. In spreadsheet it simply the value of each cell in the link matrix divided by the sum of its column. Since this is a kind of normalization, the sum of all rows at the bottom is one.
Then, we set initial value of page rank equal to the number of outbound links, that is
.
The next step is to compute the sum product
for each row.
Once we obtain the sum product, we can proceed to compute the value of page rank in the next iteration using recursive page rank formula
Figure below shows the values of the page rank computation with the sum product and initial page rank at iteration 0. Notice we put a control cell that need to be deleted to make the Excel iteration to compute the page rank.
We use Excel iteration (set Excel Options > Formulas > Enable iterative calculation > Maximum iteration = 1) as shown in the figure below.
Then you can press F9 repeatedly after deleting the control cell. MS Excel will compute the page rank. You stop pressing F9 when the value of the page ranks has been converged to some values. Notice that it does not change the value anymore and the sum of page rank is equal to the number of pages
. Here is the final result:
Spreadsheet companion of this tutorial can be downloaded here .
In the next page, you can obtain Matlab tool to compute Page Rank.
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