gibson:teaching:spring-2016:math445:lab6
====== Differences ====== This shows you the differences between two versions of the page.
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gibson:teaching:spring-2016:math445:lab6 [2016/02/24 20:43] gibson |
gibson:teaching:spring-2016:math445:lab6 [2018/03/06 06:58] (current) gibson |
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| Compute the Google Page Rank for a network of 100 pages within ''www.unh.edu''. | Compute the Google Page Rank for a network of 100 pages within ''www.unh.edu''. | ||
| - | **(a)** Go to the website [[http://www.mathworks.com/moler/chapters.html|Numerical Computing with Matlab]] by Clive Moler and download the “surfer.m” program. Set ''M=100'' and run the command | + | **(a)** Download the [[https://www.mathworks.com/matlabcentral/mlc-downloads/downloads/submissions/37976/versions/7/previews/surfer.m/index.html?access_key=|surfer.m]] Matlab script from [[http://www.mathworks.com/moler/chapters.html|Numerical Computing with Matlab]] by Clive Moler. Set ''M=100'' and run the command ''[w,L] = surfer('http://www.unh.edu',M);''. This might take a few minutes. |
| - | ''[w,L] = surfer('http://www.unh.edu',M);''. This might take a few minutes. | + | |
| **(b)** After some time this will generate a vector $w$ of websites and a matrix $L$ of links between them. All the entries of $L$ should be either 0 or 1. But $L$ will have 100^2 == 10,000 entries, so you can't check this by eye. Write a short piece of Matlab code that double-checks that all entries of $L$ are either 0 or 1. | **(b)** After some time this will generate a vector $w$ of websites and a matrix $L$ of links between them. All the entries of $L$ should be either 0 or 1. But $L$ will have 100^2 == 10,000 entries, so you can't check this by eye. Write a short piece of Matlab code that double-checks that all entries of $L$ are either 0 or 1. | ||
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| \begin{equation*} | \begin{equation*} | ||
| - | B = (1-\alpha) A + \alpha [1/M] | + | B = (1-\alpha) A + \alpha [1]/M |
| \end{equation*} | \end{equation*} | ||
| - | where $[1/M]$ is an $M \times M$ matrix of ones. Rumor has it that Google uses $\alpha = 0.15$, so use that value and calculate $B$. | + | where $[1]$ is an $M \times M$ matrix of ones. Rumor has it that Google uses $\alpha = 0.15$, so use that value and calculate $B$. |
| **(e)** Double-check that the sum of each column of $B$ is 1. Again, be clever and get Matlab to do the work, rather than listing out the sums of all the columns and verifying manually that each of the 100 numbers is 1! | **(e)** Double-check that the sum of each column of $B$ is 1. Again, be clever and get Matlab to do the work, rather than listing out the sums of all the columns and verifying manually that each of the 100 numbers is 1! | ||
| Line 48: | Line 47: | ||
| <code> | <code> | ||
| N=40; | N=40; | ||
| - | for m=1:N; | + | for n=1:N; |
| p=B*p; | p=B*p; | ||
| end | end | ||
gibson/teaching/spring-2016/math445/lab6.1456375395.txt.gz · Last modified: 2016/02/24 20:43 by gibson
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