lecture17-linkanalysis-handout-6-per

From it compute a lel eigenvector of p the entry ai

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Unformatted text preview: e next step?   Recall that row i of the transi*on prob. Matrix P tells us where we go next from state i.   So from x, our next state is distributed as xP   E.g., (000…1…000) means we re in state i. 1 i n More generally, the vector x = (x1, … xn) means the walk is in state i with probability xi. n ∑x i   The one aler that is xP2, then xP3, etc.   (Where) Does the converge? = 1. i =1 Introduc)on to Informa)on Retrieval Sec. 21.2.2 Introduc)on to Informa)on Retrieval How do we compute this vector? Pagerank summary   Let a = (a1, … an) denote the row vector of steady ­ state probabili*es.   If our current posi*on is described by a, then the next step is distributed as aP.   But a is the steady state, so a=aP.   Solving this matrix equa*on gives us a. Sec. 21.2.2   Preprocessing:   So a is the (lel) eigenvector for P.   (Corresponds to the principal eig...
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