Algimantas Adolfas Jucys: Difference between revisions

Revision as of 08:35, 8 June 2013

In graph theory and social network analysis, alpha centrality is a measure of centrality of nodes within a graph. It is an adaptation of eigenvector centrality with the addition that nodes are imbued with importance from external sources.

Definition

Given a graph with adjacency matrix $A_{i, j}$ the alpha centrality is defined as follows:

x = (I - α A^{T})^{- 1} e

where $e_{j}$ is the external importance given to node $j$ , and $α$ is a parameter.^[1]

Motivation

To understand alpha centrality one must first understand Eigenvector Centrality. An intuitive process to compute eigenvector centrality is to give every node a starting random positive amount of influence. Each node then splits its influence evenly and divides it amongst its outward neighbors, receiving from its inward neighbors in kind. This process repeats until everyone is giving out as much as they're taking in and the system has reached steady state. The amount of influence they have at this steady state is their eigenvector centrality. Computationally this process is called the power method. We know that this process has converged when the vector of influence changes only by a constant as follows.

x_{i} = \frac{1}{λ} A_{i, j}^{T} x_{j}

Where $x_{i}$ is the amount of influence that node $i$ carries, $A_{i, j}$ is the adjacency matrix and $λ$ happens to be the principal eigenvalue (although this is not terribly important here).

Alpha centrality enhances this process by allowing nodes to have external sources of influence. The amount of influence that node $i$ receives at every round is encoded in $e_{i}$ . The process described above should now stop when

x_{i} = α A_{i, j}^{T} x_{j} + e_{i}

Where $α$ is a constant that trades off the importance of external influence against the importance of connection. When $α = 0$ only the external influence matters. When $α$ is very large then only the connectivity matters, i.e. we reduce to the eigenvector centrality case.

Rather than perform the iteration described above we can solve this system for $x$ , obtaining the following equation:

x = (I - α A^{T})^{- 1} e

Applications

Alpha centrality is implemented in igraph library for network analysis and visualization.^[2]

Notes and references

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es:Centralidad ar:مركزية ألفا

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The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

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↑ http://igraph.sourceforge.net/doc/R/alpha.centrality.html

[1] One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting

In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang

Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules

Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.

A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running

The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more

There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang

[2] ttp://igraph.sourceforge.net/doc/R/alpha.centrality.html

[1]

[2]

@@ Line 1: / Line 1: @@
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+In [[graph theory]] and [[social network analysis]], '''alpha centrality''' is a measure of [[centrality]] of nodes within a [[Graph (mathematics)|graph]]. It is an adaptation of [[eigenvector centrality]] with the addition that nodes are imbued with importance from external sources.
+==Definition==
+Given a graph with [[adjacency matrix]] <math>A_{i,j}</math> the alpha centrality is defined as follows:
+:<math> x = (I-\alpha A^T)^{-1}e \, </math>
+where <math>e_j</math> is the external importance given to node <math>j</math>, and <math>\alpha</math> is a parameter.<ref>{{cite journal  | author = P. Bonacich, P. Lloyd  | title = Eigenvector-like measures of centrality for asymmetric relations  | url = http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VD1-43G39CH-2&_user=10&_coverDate=07%2F31%2F2001&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c7c10c464e20246d9d67970415887487&searchtype=a  | doi=10.1016/S0378-8733(01)00038-7}}</ref>
+==Motivation==
+To understand alpha centrality one must first understand Eigenvector Centrality. An intuitive process to compute eigenvector centrality is to give every node a starting random positive amount of influence. Each node then splits its influence evenly and divides it amongst its outward neighbors, receiving from its inward neighbors in kind. This process repeats until everyone is giving out as much as they're taking in and the system has reached steady state. The amount of influence they have at this steady state is their eigenvector centrality. Computationally this process is called the [[power method]]. We know that this process has converged when the vector of influence changes only by a constant as follows.
+:<math>x_i = \frac{1}{\lambda} A^T_{i,j}x_j</math>
+Where <math>x_i</math> is the amount of influence that node <math>i</math> carries, <math>A_{i,j}</math> is the adjacency matrix and <math>\lambda</math> happens to be the principal eigenvalue (although this is not terribly important here).
+Alpha centrality enhances this process by allowing nodes to have external sources of influence. The amount of influence that node <math>i</math> receives at every round is encoded in <math>e_i</math>. The process described above should now stop when
+:<math> x_i = \alpha A^T_{i,j}x_j + e_i \, </math>
+Where <math>\alpha</math> is a constant that trades off the importance of external influence against the importance of connection. When <math>\alpha=0</math> only the external influence matters. When <math>\alpha</math> is very large then only the connectivity matters, i.e. we reduce to the eigenvector centrality case.
+Rather than perform the iteration described above we can solve this system for <math>x</math>, obtaining the following equation:
+:<math> x = (I-\alpha A^T)^{-1}e \, </math>
+==Applications==
+Alpha centrality is implemented in igraph library for network analysis and visualization.<ref>http://igraph.sourceforge.net/doc/R/alpha.centrality.html</ref>
+==See also==
+* [[Eigenvector centrality]]
+==Notes and references==
+{{Reflist}}
+[[Category:Algebraic graph theory]]
+[[Category:Network analysis]]
+[[Category:Social networks]]
+[[es:Centralidad]]
+[[ar:مركزية ألفا]]

Algimantas Adolfas Jucys: Difference between revisions

Revision as of 08:35, 8 June 2013

Contents

Definition

Motivation

Applications

See also

Notes and references

Navigation menu

Algimantas Adolfas Jucys: Difference between revisions

Revision as of 08:35, 8 June 2013

Definition

Motivation

Applications

See also

Notes and references

Navigation menu

Search