augusti 19, 2007

Recension av Keith Devlin, Gary Lorden: The Numbers Behind Numb3rs: Solving Crime with Mathematics

TV-serien Numb3rs handlar om bröderna Don, FBI-agent, och den yngre brodern Charlie som är en matematikprofessor. Charlie är den egentlige "hjälten" i serien där hans matematiska begåvning (genialitet!) gör att Don kan lösa sina fall. Speciellt skoj är att matematiken i TV-serien är central och man har gjort sig möda om att göra den så korrekt som möjligt. Inte speciellt förvånande (för mina reguljära läsare) är serien en stor favorit.

Serien ska strax börja på fjärde säsongen och då passar det utmärkt att en bok om (kring) serien kommer ut. Det är matematikerna Keith Devlin och Gary Lorden som skrivit The Numbers Behind Numb3rs: Solving Crime with Mathematics (ISBN: 9780452288577) som gör en populärvetenskaplig exposé över matematiken som används i serien.

De två författarna är väl lämpade att skriva boken:
Keith Devlin, professor i matematik och är nog mest känd som Math Guy och skriver i den (populär)matematiska kolumnen Devlin's Angle (Archives). Devlin har även skrivit flera böcker (där 1988 års utgåva av Mathematics - the New Golden Age var en stor inspirationskälla för mitt matematikintresse).

Gary Lorden kände jag däremot inte till innan serien Numb3rs. Han är professor i matematik och "chief mathematics consultant" till TV-serien. Den senare rollen beskrivs t.ex. i CaltechNews-artikeln Crime and Computation.

Boken är "oteknisk" skriven och det krävs inga speciella matematiska förkunskaper (förutom sådana som normal skolgång bör ha gett). Det finns få formler/ekvationer och de som finns förklaras nästan alltid ingående.

När jag först läste om boken trodde jag att alla kapitel skulle behandla Numb3rs-relaterade saker och endast sådana. Man har istället valt en mer utökad variant och det saknas Numb3rs-koppling i några kapitel, t.ex. kapitel 5, "Image Enhancement and Reconstruction" som handlar om bildbearbetning i samband med efterverkningarna av lynchningen av Rodney King. Det görs också intressanta genomgångar av matematiken i och kring rättegångarna (som inte alls är med i TV-serien), t.ex. bevisvärdet av DNA-test och fingeravtryck samt kring urvalet av jurys. Denna utökning fungerar bra, även om det möjligen kan vara lite förledande i marknadsföringen.

En av de stora fördelarna med populärvetenskapliga böcker är att man blir inspirerad att läsa vidare i det ämne som behandlas. Tyvärr försvåras sådan vidareläsning genom att det i många kapitel inte finns några litteraturreferenser eller vidareläsningstips (det finns dock flera kapitel som har mycket referenser). Möjligen har författarna ansett att läsarna själv söker efter obekanta termer via sökmotorer eller Wikipedia. Fel approach enligt min mening.

Trots bristerna tycker jag om boken och rekommenderar den till de som också gillar TV-serien. Och rekommenderar TV-serien för den som inte sett den.

Bokens kapitel
Här är en listning av kapiteln och några kommentarer kring dem.


Se även
Devlins artikel om TV-serien NUMB3RS gets the math right.

Jag har köpt de två första säsongerna från Discshop. Tyvärr saknas här de kommentatorspår som finns i region 1-varianterna.

Recensionen New Book Explains How Math Can Help Solve Crimes finns även som pratversion inklusive författarnas (autentiskt återgivna förutsätter jag) röster.

Sajten Redhawke NUM3RS med länkar till matematiska begrepp

Dr. Andrew Nestler's Analysis of NUMB3RS

Min favoritblogg i Numb3rsiana: num3rs blog

Succén med TV-serien har även knoppat ett samarbete mellan CBS, Texas Intstrument och National Council of Teachers of Mathematics i form av sajten We All Use Math Every Day där lärare kan hämta material som kopplas till de olika avsnitten. Aktiviteter för respektive säsong (sorterad i bloggordning):
Season 1
Season 2
Season 3

Posted by hakank at 11:21 FM Posted to Böcker | Machine learning/data mining | Matematik | Social Network Analysis/Complex Networks | Comments (0)

augusti 14, 2007

Mark Buchanan: The Social Atom

Boken som här skrivs om är alltså Mark Buchanan The Social Atom: Why the Rich Get Richer, Cheaters Get Caught, and Your Neighbor Usually Looks Like You (ISBN: 9781596910133).

Det är en mycket trevlig bok som går igenom flera av de områden som intresserat mig under de senaste åren (länkar nedan görs nästan undantagsvis till egna skriveriansamlingar). Såsom

* agentbaserad modellering (multi-agent), applåder, trafikköer, panik
* spelteori, fångarnas dilemma
* Axtells och Axelrods simuleringar av sociala fenomen: hur uppstår diskriminering. (Axelrod har studerat mycket mer än fångarnas dilemma.)
* econophysics/sociophysics: dvs att använda fysikaliska modeller för att undersöka ekonomiska/sociala fenomen
* kognitiva illusioner
* Brian Arthurs El Farol-experiment som sedan extensivt studerats vidare (Minority Game).
* power laws, Paretos lag ("20% av befolkningen äger 80%") och andra om ojämlikheter. Power laws och fraktaler som fingeravtryck på komplexa fenomen. Men notera kritiken av ett aningslöst användande av power laws: Kritik kring power law-forskning.


Några saker som tas upp i boken:
- En komplicerad händelse kan ha enkla orsaker (och vice versa), vilket datasimuleringarna visar tydligt. Utifrån några enkla regler i en minivärld uppstår fenomen som är snarlika de komplexa fenomen som vi ser i vår värld.

(Jag saknar möjligen en referens till systemdynamik här för diskussion om relationer mellan dynamisk orsak och verkan.)

- Boken beskriver många experiment, såväl empiriska psykologiska/sociologiska experiment som datorsimuleringar. Datorsimuleringarna bygger mycket på enkla (ibland rent fysiska) modeller: för att förstå ett fenomen gäller det att skala av allt som inte är relevant för fenomenet. Man kan här notera att Buchanan är fysiker.

- Kritik av traditionella ekonomiska modeller: Sådana modeller tenderar av missa målet och bli ointressanta att arbeta med i praktiken, t.ex. de förutsätter att vi är fullständigt rationella varelser; att de förutsätter att sakernas tillstånd ska komma i jämvikt. Ett kännetecken på sociala fenomen är att de är dynamiska (icke-jämvikt). Vi tenderar att göra felaktiga bedömningar (kognitiva illusioner).

- Vi känneteckas att vara adaptiva, dvs vi lär oss t.ex. genom att helt enkelt starta någonstans och därefter bedöma resultatet; kanske genom imitation av andra. Mycket skrivs om just detta.

- En förutsättning för våra samhällen är vår fantastiska förmåga att samarbeta, även utan att det gynnar oss direkt (flera exempel och experiment beskrivs här). En tes som förs fram är att vi på något sätt är genetiskt skruvade till detta. Naturligtvis tas även nackdelarna med denna adaptivitet upp: krig, diskriminering, börskrascher, och andra hysterier såsom Hola-hola-ringar (eller varför inte ett mer modernt fenomen: Facebook).

- Man bör komma ihåg att de sociala modellerna som beskrivs oftast inte kan förutsäga vad som händer med en specifik individ, företag eller grupp (dvs "atom") i ett händelseförlopp. Det är snarare de statistiska sambanden som kan prognosticeras.


Några värderingar av boken
* Det är bra och lättlästa förklaringar av experiment och simuleringarna. De senare är översiktligt beskrivna emellanåt så man måste gå till källorna för att få mer detaljer (vilket säkert är meningen).

* Introduktionen till kapitlen är beskrivning av en aktuell eller känd företeelse (t.ex. olika krig eller oroshärdar) som sedan används som inramning för kapitlet. Detta programmatiska upplägg känns ibland krystat.

* Boken har en notapparat där de flesta källorna finns och där fotnoten är tydligt markerad i löptexten. (Sådant råkar jag tycka vara viktigt i PopSci-litteratur.)

* Jag blev faktiskt förvånad av att det pratades väldigt lite specifikt om small world-fenomenet.


Det näst sista omdömet: Även om jag läst en hel del av det som avhandlas i boken var den inspirerande att läsa, framför allt kring de många simuleringar som gjorts. En del av de mer ekonofysiska experimenten kände jag inte till så det ska bli skoj att gå till källorna där. Alternativt att läsa om Schelling, Axelrod och Axtell.


Slutligen: En bok vars introduktion börjar med Thomas Schelling (mer specifikt dennes nydanande modell av segregering) kan helt enkelt inte vara dålig.


Bokblogg finns naturligtvis, finurligt nog döpt som boken The Social Atom. Se t.ex. The physics of crowds.

Buchanan har även skrivit boken Nexus om komplexa nätverk.


Tidigare skrivet här om Mark Buchanan
Social Network Analysis och Complex Networks - En liten introduktion

Trender fungerar som magneter?

Hur mycket väger pengar? - Nu även med lite granularitetsforskning

Komplexa system och software engineering


Och apropå det så beställdes i morse biografin över Schelling Thomas Schelling And The Nuclear Age - Strategy as Social Science (ISBN: 9780714685441).

Posted by hakank at 09:56 EM Posted to Agentbaserad modellering | Kognitiva illusioner | Komplexitet/emergens | Social Network Analysis/Complex Networks | Spelteori och ekonomi | Comments (2)

juli 13, 2006

Social nätverksanalys av passningar i fotbolls-VM

Jag trodde att det skulle vara slut med skrivningar om fotbolls-VM. Så var tydligen inte fallet.

Via visual complexity (via mailinglistan SOCNET) hittades bilder från en social nätverksanalys av passningar i vissa matcher i fotbolls-VM.

Här (JPG) är en en bild över final-matchen. Just större pil desto starkare är kopplingen. Storleken på noden ("ploppen" för spelaren) anger betweenness, ett mått på hur viktig spelaren är som "förmedlare" av bollen ("broker" på engelska, se t.ex. förklaringen här).


Se även
Lista över andra matcher med liknande bilder. T.ex. Tyskland - Sverige-matchen (klicka på bilden för att förstora den).
En tidigare samling från samma sajt som föregående
Netzwerkanalyse und die Fußballweltmeisterschaft - Network Analysis and the soccer worldcup, t.ex. matchen Tyskland - Sverige (JPG).


Social Network Analysis och Complex Networks - En liten introduktion
Kategorin Social Network Analysis/Complex networks
Ytterligare forskning kring fotboll.


Andra bloggar om: , .

Posted by hakank at 09:57 FM Posted to Social Network Analysis/Complex Networks | Sport, idrott, hälsa | Comments (0)

december 30, 2005

Rappares sociala nätverk

(Not: Måste erkänna att jag är väldigt underkompetent när det gäller rap-musik och vissa termer kan därför vara felaktiga.)


Plus Magazine rapporterar i Rap: rivalry and chivalry om en undersökning av rappares sociala nätverk, dvs vilka som spelat/sjungit tillsammans med varandra. Philip Ball skriver om samma undersökning i Does rivalry rewire the rapping web?.

Det visar sig att detta sociala nätverk har två ovanligare egenskaper:

* Det är ett ganska tätt nätverk till skillnad från andra sociala nätverk, där många gör gästspel hos andra: Tidigare jazzmusik kännetecknades också av en sådan täthet (se refererns till paper nedan).

Mer tekniskt är ett tätt nätverk då medlemmarna är kopplade till varandra med en låg "grad av separation" (degrees of separation, har låg diameter), dvs att man har spelat/sjungit med varandra direkt eller spelat med någon som spelat med någon, osv i ett fåtal steg. För rappare är den genomsnittliga graden 2.9, till skillnad från t.ex. högenergifysiker som har samarbetat med varandra med diametern 5.9.

* Dessa nätverk har låg assortativitet (assortativity), dvs att de mest kopplade personerna tenderar inte att vara kopplade tillvarandra, till skillnad från många andra social nätverk.

Så här skriver Plus Magazine:


Assortativity measures the extent to which links exist between highly connected nodes and those much less connected. In assortative networks, well-connected individuals tend to be linked to each other. This makes perfect sense in most social networks — someone who is particularly sociable and friendly is very likely to also know the other most sociable people. But for some reason, the rap network has a very low level of assortativity — the most prolific rappers do not on the whole appear on each other's albums. One reason Smith suggests for this is that the rap market is highly competitive, and successful artists may be reluctant to help the sales of their adversaries. Smith thinks though that the full explanation goes deeper than simple commercial interests. The rap world is known to be fraught with particularly deep rivalries. Artists are often heard challenging and taunting each other on their records, and enmities in the past have escalated to violence and even murder. One particularly notorious rivalry arose between Death Row Records in Los Angeles (the "West Side") and Bad Boy Records in New York (the "East Side").


Artikeln som refereras är Reginald D. Smith The Network of Collaboration Among Rappers and its Community Structure (PDF)
Abstract:


The social network formed by the collaboration between rappers is studied using standard statistical techniques for analyzing complex networks. In addition, the community structure of the rap music community is analyzed using a new method that uses weighted edges to determine which connections are most important and revealing among all the communities. The results of this method as well as possible reasons for the structure of the rap music community are discussed.


Se även
Reginald Smith
Rap Collaboration Network Explanation där det bl.a. finns en kort FAQ för hur Smith gjort sin forskning.

Om tidigare jazzmusikens täthet, se Pablo Gleiser, Leon Danon Community Structure in Jazz (PDF)

Samt Social Network Analysis och Complex Networks - En liten introduktion
och för den delen andra anteckningar i kategorin Social networks analysis/complex networks.

Posted by hakank at 08:52 FM Posted to Musik | Social Network Analysis/Complex Networks | Comments (0)

oktober 31, 2005

Nytt nummer av JASSS (Journal of Artificial Societies and Social Simulation)

JASSS (Journal of Artificial Societies and Social Simulation) har kommit ut med ett nytt nummer, Volume 8, Issue 4. För en kort presentation av tidskriften, se Journal of Artificial Societies and Social Simulation.

Detta nummer har några intressanta artiklar.

Josep M. Pujol, Andreas Flache, Jordi Delgado, Ramon Sangüesa
How Can Social Networks Ever Become Complex? Modelling the Emergence of Complex Networks from Local Social Exchanges
Abstract:

Small-world and power-law network structures have been prominently proposed as models of large networks. However, the assumptions of these models usually lack sociological grounding. We present a computational model grounded in social exchange theory. Agents search attractive exchange partners in a diverse population. Agent use simple decision heuristics, based on imperfect, local information. Computer simulations show that the topological structure of the emergent social network depends heavily upon two sets of conditions, harshness of the exchange game and learning capacities of the agents. Further analysis show that a combination of these conditions affects whether star-like, small-world or power-law structures emerge.

Vilket kanske kan ses som en pendang till Kritik kring power law-forskning.


Chung-Yuan Huang, Chuen-Tsai Sun and Hsun-Cheng Lin
Influence of Local Information on Social Simulations in Small-World Network Models
Abstract

As part of Watts and Strogatz's small-world model of complex networks, local information mechanisms such as landscape properties are used to approximate real-world conditions in social simulations. The authors investigated the influence of local information on social simulations based on the small-world network model, using a cellular automata variation with added shortcuts as a test platform for simulating the spread of an epidemic disease or cultural values/ideas. Results from experimental simulations show that the percentage of weak individuals should be considered significant local information, but vertex degree influences and the distribution patterns of weak individuals should not. When exploring contagion problems, the results encourage a future emphasis on setting and the proportions of specific values of local information related to infection strength or resistance, and a reduced emphasis on the detailed topological structure of small-world network models and the distribution patterns of specific values of local information.


Det finns även flera artiklar på temat Epistemological Perspectives on Simulation .

Posted by hakank at 06:40 EM Posted to Agentbaserad modellering | Social Network Analysis/Complex Networks | Comments (0)

oktober 29, 2005

Kritik kring power law-forskning

Några korta länkningar till en intressant kritik av power law-forskningen och speciellt av Albert-László Barabasi (som jag skrivit om en del tidigare).


Joao Gama Oliveira och Albert-László Barabási skrev nyligen Darwin and Einstein correspondence patterns (PDF, Complementary Materials). New Scientist skrev sedan om detta i Email and letter writing share fundamental pattern. Jämför med Barabasis The origin of bursts and heavy tails in human dynamics (PDF, dess Supplement) som undersöker hur mail skickas och besvaras mellan en flera personer.)


Här är några aktuella och tidigare kritiska röster kring power law-forskningen. "Huvudpersonerna" är två statistiska fördelningar:
Log normal
Power law
"Normal" som Shalizi skriver om i citatet nedan är Normal distribution.


Cosma Shalizi: Gauss Is Not Mocked:

[T]he apparent power law is merely an artifact of a bad analysis of the data, which which is immensely better described by a log-normal distribution.

...

Log-normals are very common, for the same reasons that normals are. Unlike normals, they are very easy to mistake for power law distributions, especially if your knowledge of statistics is as limited as most theoretical physicists'. (The distribution of links to weblogs, for instance, is much better fit by a log-normal than a power law, as we've seen.)


Cosma Shalizi: Speaking Truth to Power About Weblogs, or, How Not to Draw a Straight Line.

Daniel B. Stouffer, R. Dean Malmgren, Luis A. N. Amaral: Comment on Barabasi, Nature 435, 207 (2005)

Michel L. Goldstein, Steven A. Morris, Gary G. Yen: Problems with Fitting to the Power-Law Distribution

Aaron Clauset: Links, links, links.

Pharyngula: λ >> µ, or why I haven't answered you yet

Geomblog: Darwin's and Einstein's (e)mail correspondence rates, or a rumination on power laws.


Michael Mitzenmacher har skrivit en översikt över power-law-forskningen: A Brief History of Generative Models for Power Law and Lognormal Distributions (PDF, publicerad i Internet Mathematics, volume 1); en tidigare version PS), och berättar i en videoföreläsning sina egna åsikter om denna forskning: New Directions for Power Law Research, där själva videoströmningen (QuickTime) finns här. (Från Models of Real-World Random Networks med en massa andra intressanta videos.)

Se även B. Conrad and M. Mitzenmacher Power Laws for Monkeys Typing Randomly: The Case of Unequal Probabilities (PDF).

Posted by hakank at 10:03 FM Posted to Social Network Analysis/Complex Networks | Statistik/data-analys | Comments (0)

oktober 19, 2005

The Dynamics of Viral Marketing

Jurij Leskovec, Lada A. Adamic, Bernardo A. Huberman: The Dynamics of Viral Marketing (PDF, 39 sidor)

Abstract (min fetning)

We present an analysis of a person-to-person recommendation network, consisting of 4 million people who made 16 million recommendations on half a million products. We observed the propagation of recommendations and the cascade sizes, which can be explained by a stochastic dynamic model. We then established how the recommendation network grows over time and how effective it is from the viewpoint of the senders and receivers of recommendations. While on average recommendations are not very effective at inducing purchases and do not spread very far, there are product and pricing categories for which viral marketing seems to be very effective.


Saxat från texten (min fetning):

Our analysis focuses on the recommendation referral program run by a large retailer. The program rules were as follows. Each time a person purchases a book, music, or a movie he or she is given the option of sending emails recommending the item to friends. The first person to purchase the same item through a referral link in the email gets a 10% discount. When this happens the sender of the recommendation receives a 10% credit on their purchase.

This study is novel in that we are able, for the first time, to directly observe the effectiveness of person to person word of mouth advertising for hundreds of thousands of products. We can see what kind of product is more likely to be purchased as a result of this type of recommendation, as well as describe the size of the cascade that results from an initial purchase and subsequent recommendations.

Se även
Liknande undersökningar på HP Labs.

Posted by hakank at 08:50 EM Posted to Rekommendationssystem | Social Network Analysis/Complex Networks | Comments (0)

oktober 05, 2005

Robert Mertons artikel om Matteus-principen

Matteus-principen (eller effekten) är "åt den som har ska vara givet", dvs att den som redan har mycket av något kommer att få mer, och som en konsekvens av detta kommer de som har lite får mindre (av den totala kakan). Namnet kommer från Matteusevangeliet och förklars bibliskt här (länk till Svenska Kyrkan).

Principen sammanfattar resultatet av många sociala fenomen, speciellt de som bygger på sociala nätverk: De som redan har kontakter, pengar eller många länkar till sin blogg tenderar att få mer och mer, i en allt växande orättvisa. Orättvist eller inte så fungerar vi tydligen så.

I flera av de skrivningar som hamnat i Social Network Analysis/Complex Networks beskrivs sociala nätverk och framförallt komplexa nätverk där man studerar denna typ av fenomen hos grupper. Endast undantagsvis har Matteus-principen nämnts vid namn Ett undantag är Brian Arthur: Lock-in och El Farol.

Däremot har jag inte läst Robert Mertons ursprungliga artikel The Matthew Effect in Science (PDF) där begreppet myntades. (Artikeln är dock fortfarande oläst.)


Det var just hittandet av denna skrift (via Jason Kottke) som föranledde denna bloggning just nu. Varför man nu måste redogöra för sina skäl att skriva något på sin egen blogg...

Posted by hakank at 07:36 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

augusti 25, 2005

Juyong Park, M. E. J. Newman:: A network-based ranking system for American college football

Juyong Park, M. E. J. Newman: A network-based ranking system for American college football (PDF)



American college football faces a conflict created by the desire to stage national championship games between the best teams of a season when there is no conventional playoff system to decide which those teams are. Instead, ranking of teams is based on their record of wins and losses during the season, but each team plays only a small fraction of eligible opponents, making the system underdetermined or contradictory or both. It is an interesting challenge to create a ranking system that at once is mathematically well-founded, gives results in general accord with received wisdom concerning the relative strengths of the teams, and is based upon intuitive principles, allowing it to be accepted readily by fans and experts alike. Here we introduce a one-parameter ranking method that satisfies all of these requirements and is based on a network representation of college football schedules.


En inte särskilt seriös jämförelse är Herbert Wilf Searching the web with eigenvectors (PDF) som använder rankning i en fotbollsturnering för att förklara googles metod att räkna ut PageRank. (Förgäves har jag försökt att få in detta trevliga paper i tidigare blogganteckningar. :)


Enligt Gustav Holmberg och andra har arxiv.org nu blivit med trackbacks. Får se om/hur det funkar.

Posted by hakank at 10:46 EM Posted to Social Network Analysis/Complex Networks | Comments (1)

juli 22, 2005

Math Matters videoföreläsningar

Som tidigare skrivits tycker jag om videoföreläsningar i matematisk kopplade ämnen (och naturligtvis även andra ämnen i intressesfären). Via MathForge hittades idag Math Matters IMA Public Lecture Series.

Där finns t.ex.
* James D Murray: The Marriage Equation - A Practical Theory for Predicting Divorce and a Scientifically-Based Marital Therapy, den teori om olika typer av giftermål som Murray beskriver i boken Mathematics Of Marriage - Dynamic Nonlinear Models (Bokus, ISBN: 0262572303) skriven tillsammans med John M Gottman (Gottman står som huvudförfattare). Murray har också ett kapitel om detta i sin Mathematical Biology - Spatial Models and Biomedical Applications (Bokus, ISBN: 0387952284). Malcolm Gladwell skrev också en del om teorin i sin Blink (Bokus, ISBN: 0316001058. Cf t.ex. min recension av denna bok.)

* Steven Strogatz: Sync: The Emerging Science of Spontaneous Order. Strogatz har skrivit en intressant populärvetenskaplig bok om just detta Sync (Bokus, ISBN: 0786887214) - som jag märkligt nog inte recenserat men rekommenderar storligen - men framförallt skrivit den fantastiska läroboken om dynamiska system Nonlinear Dynamics and Chaos - With Applications to Physics, Biology, Chemistry and Engineering (Bokus, ISBN: 0738204536). Se även kategorierna Komplexitets/emergens och Social network analysis/complex networks där Strogatz nämns från tid till annan. I föreläsningen får man bl.a. se den eldflugors synkronisering, ett fenomen som väl kan ses som paradigmfallet av synkronisering och var det som fick Strogatz (tillsamman med Duncan Watts) att studera komplexa nätverk.

* Benoit Mandelbrot: Fractals/Multifractals in Finance, the Internet & Other "Wild" Aspects of Man's Works

* Richard A. Tapia: Math at Top Speed: Breaking Myths in the Drag Racing Folklore

* Bruce Schneier: Natural Laws of Digital Content: the Folly of Copy Protection on the Internet


Se även Recordings of IMA Talks som innehåller ett flertal föreläsningar i diverse ämnen, vad jag kan se inte alls lika populariserande hållna.

I samma anda kan här rekommenderas MIT:s OpenCourseWare som har vissa videoföreläsningar, bl.a. den som just nu tar upp en hel del av min tid: Differential Equations med föreläsaren Arthus Mattuck.

Posted by hakank at 07:33 FM Posted to Agentbaserad modellering | Komplexitet/emergens | Matematik | Social Network Analysis/Complex Networks | Comments (0)

juli 12, 2005

New Scientist: Email forwarding amounts to ritual gift exchange

New Scientist: Email forwarding amounts to ritual gift exchange (min fetning):

Forwarding a quirky email or an amusing link or video attachment to colleagues may seem innocent enough, but it is the modern equivalent of ritual gift exchange and carries with it similar social implications, say US researchers. ... Benjamin Gross at the University of Illinois, US, and colleagues studied email forwarding behaviour by conducting informal interviews among email users. He says forwarding emails plays a vital role in constructing and maintaining modern social ties, despite the phenomenon receiving scant attention from social scientists.

Forwarding a genuinely amusing or interesting link to a friend, for example, shows that you are thinking of them and are aware of the sort of content they like, Gross says. But passing an irrelevant or out-of-date link on to contacts can be annoying, thus lowering the sender's social status in the recipient’s eyes.


På samma sätt fungerar det troligen med de länkar man skriver på sin blogg, i alla fall för länkbloggningar. Om det är en lite äldre länk verkar rätt många bloggare brasklappa med "ja, jag vet att jag troligen är sist med detta. Men ...". Just för att inte få sin sociala status sänkt.


Se även
Benjamin Gross och hans (tillsammans med Marc Smith och Jeff Ubois) artikel Forward Thinking" (PDF). Jeff Ubois har skrivit en artikel kring detta i Messaging News (PDF, sidan 24). Uppdatering: Artikeln "Forward Thinking" finns nu online.

(Marc Smith nämndes för övrigt här för ett tag sedan, i Microsofts egen sociolog.)


Det mail-analyssystem som beskrivs i NS-artikeln är Forward Track och det har jag inte hört talas om tidigare (och det finns ingen svensk förekomst på google heller). Så här beskrivs det:

ForwardTrack is a new system created by Eyebeam R&D (redeveloped with the assist from Stamen Design) designed to promote on-line activism. The system tracks and maps the diffusion of email forwards, political calls-to-action, and online petitions. It can trace email forwards, map the impact of blogs, and facilitate web-based sign-ups and social networking. Our goal is to help people understand decentralized networks and see the power of "6 degrees of separation." ForwardTrack technology helps prove that one person can make a difference.

Det är fritt att ladda ner och kräver PHP och MySQL.

Posted by hakank at 10:20 EM Posted to Social Network Analysis/Complex Networks | Comments (1)

juni 15, 2005

Nature News: Modellers measure 'word of mouth' for films

Nature News: Modellers measure 'word of mouth' for films

It's official, says one group of researchers: Blade II is a bad film. Their study turns patterns of attendance into a single number that claims to grade a film's quality.

The number attempts to gauge of how good the 'word of mouth' was around a given film, based on the behaviour of the harshest critics of all, the paying public.

César Hidalgo, now a graduate student in physics at the University of Notre Dame, Indiana, and his colleagues, decided to study the 'word of mouth' effect in the film world simply because reviews often have a huge impact on audience numbers and there are copious data on ticket sales.


Se vidare
Cesar A. Hidalgo, Alejandra Castro, Carlos Rodriguez-Sickert: The effect of social interactions in the primary life cycle of motion pictures (arXiv, PDF)

Abstract:

We model the consumption life cycle of theater attendance for single movies by taking into account the size of the targeted group and the effect of social interactions. We contrast the model with empirical data from the film industry obtaining good agreement with the diverse types of behaviors empirically found in the data. The model grants a quantitative measure of the valorization of this cultural good based on the relative values of the coupling between agents who have watched the movie and the ones who have not.

Posted by hakank at 06:22 EM Posted to Social Network Analysis/Complex Networks | Comments (1)

juni 13, 2005

"Det tar tid att bygga sociala nätverk"

Thom Singer ( The Business Development / Networking Blog: A discussion about the importance of building a network, creating your professional brand, embracing marketing and fine tuning sales skills.) skriver i Building a Network Takes Time...Be Patient om en diskussion med en bekant som vill bli (er)känd som expert i sitt fält (min emfas):

I was recently having a discussion with a friend who wants to grow his reputation in his industry, and desires to be seen as one of the local "experts" in his field.

...

In the course of our ninety-minute meal together, I listened to his hopes of becoming a well recognized name and was surprised by the short time frame that he thought this could be accomplished. He felt that if he focused on networking for a few months, that by the end of the summer he could be seen as the "Go To Person".

...

To start, he looked at the whole process as something that could benefit his career. Never once, even when I brought it up, did he address what he could do to assist others in his network. His whole focus was on growing his own reputation with the end result being more business for his company. If your motives are selfish, then your return on the time invested in networking will be limited. You must see the "give and take" relationship of networking, and be committed to give more than you get. Especially in the beginning.

Posted by hakank at 07:32 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

Characterization of complex networks: A survey of measurements

Luciano da F. Costa, Francisco A. Rodrigues, Gonzalo Travieso, P. R. Villas Boas: Characterization of complex networks: A survey of measurements (arXiv, PDF) är en genomgång av olika metriker (measurments) och metoder inom forskningen kring komplexa nätverk.

Abstract:

Each complex network (or class of networks) presents specific topological features which characterize its connectivity and highly influence the dynamics and function of processes executed on the network. The analysis, discrimination, and synthesis of complex networks therefore rely on the use of measurements capable of expressing the most relevant topological features. This article presents a survey of such measurements. It includes general considerations about complex network characterization, a brief review of the principal models, and the presentation of the main existing measurements organized into classes. Depending on the network and the analysis task one has in mind, a specific set of features may be chosen. It is hoped that the present survey will help the identification of the most suitable measurements.

Komplementsajt till ovanstående: Resources in Complex Networks som innehåller sådant som referenser till böcker, datamängder och mjukvara inom området.

Posted by hakank at 06:13 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

maj 18, 2005

Musikdelning mellan kolleger: sociala avigsidor och möjligheter

Mer intressanta studier.

New Scientist Digital music-sharing stirs social tensions berättar om en studie kring arbetskollegers delning av musik via nätverk. Jag vet inte om det är så farligt, men det är intressant att man försöker att skapa en "persona" med sin musiksmak.

Sharing a digital music collection with co-workers can be fraught with social perils, a study of US office workers has revealed.
...
Participants confessed to forming judgements about co-workers based on the taste - or lack of taste - revealed by their music collection. Many also admitted to tailoring their own music library to project a particular persona, and some said they deliberately hid particularly embarrassing tracks from others.
...
Participants also took great care selecting the songs included in their collection. For example, one admitted to copying new CDs just to make his personal music library seem more "balanced".


Tydligen så sökte man inte efter ny musik utan låtar man känner igen. Sociologen Mike Ayers (som har bloggen Michael D. Ayers) kommenterar att detta could be compared to scanning someone's CD collection and picking out something you're familiar with.

Om möjligheterna i allt detta kommenterar Ayers med:

Ayers suggests that personal playlists linked to online music stores could eventually prove very popular. "You can create your own iTunes playlist for people to buy," he adds. "I think that's revolutionary, in terms of the technology, public space, capital, and sharing taste."


Studien som refereras är Amy Voida: Listening in: Practices surrounding iTunes music sharing (PDF).

Abstract:
This paper presents a descriptive account of the social practices surrounding the iTunes music sharing of 13 participants in one organizational setting. Specifically, we characterize adoption, critical mass, and privacy; impression management and access control; the musical impressions of others that are created as a result of music sharing; the ways in which participants attempted to make sense of the dynamic system; and implications of the overlaid technical, musical, and corporate topologies. We interleave design implications throughout our results and relate those results to broader themes in a music sharing design space.

Posted by hakank at 07:44 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

Komplex-nätverksanalys av röstningar i Eurovision Song Contest

How does Europe 'Make Its Mind Up'? Connections, cliques, and compatibility between countries in the Eurovision Song Contest, av Daniel Fenn, Omer Suleman, Janet Efstathiou, Neil F. Johnson, är en komplex-nätverksanalys av röstbeteendet i Eurovision Song Contest.

Abstract
We investigate the complex relationships between countries in the Eurovision Song Contest, by recasting past voting data in terms of a dynamical network. Despite the British tendency to feel distant from Europe, our analysis shows that the U.K. is remarkably compatible, or 'in tune', with other European countries. Equally surprising is our finding that some other core countries, most notably France, are significantly 'out of tune' with the rest of Europe. In addition, our analysis enables us to confirm a widely-held belief that there are unofficial cliques of countries -- however these cliques are not always the expected ones, nor can their existence be explained solely on the grounds of geographical proximity. The complexity in this system emerges via the group 'self-assessment' process, and in the absence of any central controller. One might therefore speculate that such complexity is representative of many real-world situations in which groups of 'agents' establish their own inter-relationships and hence ultimately decide their own fate. Possible examples include groups of individuals, societies, political groups or even governments.


Introducerande artikel till studien
Plus Magazine-artikeln United Kingdom - twelve points skriver introducerande om studien:

The European Song Contest is a perfect example of what mathematicians call a complex system. This consists of a group of objects (countries) which interact with each other (by giving each other points for their songs), and this interaction can be tracked over time. A statistical analysis of the system can then give some insight in the nature of the interaction. For example, it can show whether certain countries form cliques that always vote similarly, or whether a country's voting is largely "in tune" with that of the whole group.
...
One such test, which the scientists say is new, involves seeing whether voting relationships between countries persists over time. If, for example, country A gives and/or receives points from another country B over a long period of time, then we can deduce that in some way the musical tastes of the two countries are related. Carrying out the same analysis between country A and all other countries in turn will show whether or not country A is "in tune" with the rest of Europe.

Slutsatsen beskrivs på följande sätt:


And the results of the study? [...] [I]t is the UK that seems largely in tune with the rest of Europe, while France stands slightly askew. France's isolation is expressed further by the fact that it does not belong to any of the cliques identified by the study. These include the usual suspects, such as Greece and Cyprus, the UK and Ireland, and the Nordic countries, but also more surprising pairings such as Croatia and Malta, which are not geographically close.


Sverige, då?
Hur är det då med Sverige? T.ex. finns det en - inte speciellt förvånande - stark röstkorrelation mellan Sverige och Danmark; endast Cypern-Grekland har ett starkare band. Sedan klustrar vi med - i ordning - Island, Estland (!), Norge och Finland (se vidare dendogrammet på sid 7, figur 5).


Se även
Memetisk analys av röstningar i Schlagerfestivalen som beskriver en annan undersökning av Eurovision Song Contest utifrån röstningarna.


Uppdatering
På Crooked Timber skrivs mer om undersökningen. Isolated social networkers är kritisk till fysiker som uppfinner social nätverksanalys på nytt, och det finns en intressant bild av citeringar av forskningen inom sociala nätverk resp. social nätverksanalys som visar en stor isolering mellan de två områdena. Man hänvisar även till Kieran Healy som gjorde en liknande undersökning kring Eurovison Song Contest för ett år sedan: Torture of a different kind.

Uppdatering 2
Några fler som skrivit om detta.
Philip Ball i Nature: Physicists uncover Eurovision biases
Cosma Shalizi (bloggen Three-Toed Sloth): Networks and Netwars

Posted by hakank at 06:05 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

april 12, 2005

Duncan Watts om komplexa nätverk och Steve Borgatti om sociala nätverk

Två Taicon (The Trans-Atlantic Initiative on Complex Organizations and Networks)-föreläsningar i ett.

Duncan Watts börjar med att prata om forskning inom komplexa nätverk i Six Degrees: The Science of a Connected Age. Föredrag börjar cirka 10 minuter in i bandet, efter lite olika introduktioner.

Sedan talar Steve Borgatti om forskning inom sociala nätverk som en kommentar till Watts föreläsning. Lite märkligt att det inte står något om hans föreläsning på sajten. Borgatti är - forutom f.d. ordförande i INSNA (International Network for Social Network Analysis) - även skapare att det kompetenta programmet Ucinet, ett av mina två favoritprogram för sådana analyser. (Pajek är det andra favoritprogrammet.)

I morgon (13 mars 2005, 18:15 lokalt Zürich såvitt jag förstått) håller John Holland ett föredrag om Agents: Specializations for Language. Det ska bli intressant.


För vidare inom om komplexa och sociala nätverk, se även kategorin Social Network Analysis and Complex Networks samt samlingssidan Social Network Analysis och Complex Networks - En liten introduktion.

Posted by hakank at 11:20 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

mars 20, 2005

Word of Mouth samt en ovidkommande gåta

Som N/ (**) på Researcher skrev häromdagen i Consumer marketing: Aldrig förut har så mycket data funnits när det gäller mun-till-mun-marknadsföring/word of mouth..

Mitt intresse för Word of Mouth-fenomenet är egentligen inte så mycket marknadssmässiga utan mer den sociala aspekten av fenomenet som t.ex. beskrivs i Malcolm Gladwells The Tipping Point, och diskussioner kring sociala nätverk etc. (Boken finns att köpa på Bokus. Se även min recension .)

Kanske ännu mer är det dataanalyssidan av fenomenet som fascinerar: hur mycket av omdömena, tyckandena och länkarna som finns i bloggar, mailinglistor och andra onlineforum skulle man kunna använda för att kunna göra automatiska Word of Mouth-rekommenderare (om nu inte detta begrepp är en oxymoron)?). Det blir då en utökning av de mer traditionella rekommendationssystem, men mer om det till en annan gång. (En av de mest kända skrifterna inom detta områdena kring detta heter f.ö. Social Information Filtering: Algorithms for Automating "Word of Mouth, skriven av Upendra Shardanand and Pattie Maes.)


Via Proven Ways to Get New Customers (tagline: "Ideas and Analysis from an Executive Recruiter who speaks with dozens of America's top Marketing VP's every week.") hittades ett ställe som verkar ha mycket matnyttigt inom word of mouth-området: Word of Mouth Marketing Association (WOMMA).

Här är några av de - för mig - mer intressanta sidorna.
* Womma Library med flera intressanta boktips och artiklar.
* En sammanfattning av olika WoM-tekniker beskrivs i Word of Mouth 101 (PDF).
* Womma har också en blogg: Womnibus. Namnet definieras på följande sätt: (Def: n: a collection of knowledge about word of mouth marketing; from 'word-of-mouth omnibus') Your central resource for learning about word of mouth marketing.
Länkar till olika RSS-flödena finns här.


Not:
Åsk på Adland skriver en hel del om word of mouth-marknadsföring liksom DurnikBlog ("Nyheter, åsikter och idéer om Permission Marketing & Word of Mouth - och annat intressant i marknadsföring").


Ett ganska ovidkommande sidospår eller "N:s mystiska symboler"
** Sagda Åsk berättade häromdagen att N:s kommentarssignatur är ett "N" följt av ett "|"-tecken (pipe-tecken) och inte ett "J" (ji) som jag tidigare trott. Däremot berättade Åsk inte varför detta tecken används, och jag blev naturligtvis nyfiken.

Kanske ska det tolkas som "N talar" eller något liknande, dvs som i de kommandon man ger via kommandorader för att skicka data (filtrera) mellan olika program, vilket ju är en fin symbol för att kommunicera med sina läsare.

Men mysteriet är mer mystiskt än så: "N|" används som signatur i kommentarerna, men en annan symbol: "N/" används som signatur i själva blogganteckningen. Själv använder jag "/hakank/" som markering på bl.a. mina matpaket för att signalera ägandeskapet (och som kommer från loggan för ett företag inom webbutvecklingsbranschen som skapades kring 1996, där "/" naturligtvis ska associera till webbens URL:ar), men varför ett "/"?

Hmm, kan det vara början på ASCII-snurran, dvs tecknen "|", "/", "-", "\", som avses? Det kanske finns ett "N-" och "N\" någonstans som jag inte hittat...

Posted by hakank at 07:37 EM Posted to Social Network Analysis/Complex Networks | Comments (7)

november 30, 2004

Nathan LaBelle, Eugene Wallingford: Inter-Package Dependency Networks in Open-Source Software

Nathan LaBelle, Eugene Wallingford: Inter-Package Dependency Networks in Open-Source Software
Abstract:
This research analyzes complex networks in open-source software at the inter-package level, where package dependencies often span across projects and between development groups. We review complex networks identified at "lower" levels of abstraction, and then formulate a description of interacting software components at the package level, a relatively "high" level of abstraction. By mining open-source software repositories from two sources, we empirically show that the coupling of modules at this granularity creates a small-world and scale-free network in both instances.


Man avslutar med följande konklusion och diskussion:

This research has shown that package dependency networks mined from two open-source software repositories share the following properties typical to other real-world networks:
• The small-world effect: short geodesic path lengths and high clustering.
• Near power-law distribution of edges.
• The presence of a giant component, [....]

There are many directions for future research in the study of software networks. Currently, there is no model of network formation that takes software dynamics (reuse, refactoring, addition of new packages) in to account. Also, the impact of the network structure on software dynamics should be investigated. Future research should identify other networks in software and move towards formulating a theory of networks and their value to software engineering. Additional dependency networks can be constructed on Windows computers using memory profiling tools, and determining interactions based on shared .DLL (Dynamic Library Link) files and Active-X controls.

Jämför t.ex. med Komplexitet i mjukvaruarkitektur.

Posted by hakank at 07:30 FM Posted to Social Network Analysis/Complex Networks | Comments (0)

oktober 14, 2004

Tracing the Evolution of Social Software

Life With Alacrity: Tracing the Evolution of Social Software

The term 'social software', which is now used to define software that supports group interaction, has only become relatively popular within the last two or more years. However, the core ideas of social software itself enjoy a much longer history, running back to Vannevar Bush's ideas about 'memex' in 1945, and traveling through terms such as Augmentation, Groupware, and CSCW in the 1960s, 70s, 80s, and 90s.

By examining the many terms used to describe today's 'social software' we can also explore the origins of social software itself, and see how there exists a very real life cycle concerning the use of technical terminology.

Via danah boyd.

Posted by hakank at 07:17 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

augusti 13, 2004

Hur svårt är det att hitta i städer?

I Nature News-artikeln The urban maze skriver Philip Ball om två undersökningar kring hur komplicerade städer är, bl.a. en där några svenska städer (Stockholm, Malmö, Umeå) har studerats.

[Martin] Rosvall, of Umea University in Sweden, and his co-workers have tried to figure out why it is so hard for us to find our way around cities. Of course, the obvious answer is that cities have a lot of streets. And particularly if you live in an old city like London or Athens, those streets are messily arranged. But it turns out that the problem is a lot worse than that.

One way of gauging the complexity of a city is to ask how many directions you would need to get around. This need not be a function of distance: major arteries through a city can channel you efficiently between remote locations. In terms of information, any road off such a main highway is the same distance away from a particular point as any other ('second on the left' is no more complex an instruction than 'tenth on the left').
...
The real cities were consistently harder to navigate than the randomized ones, in other words the 'search information' needed on average to navigate between two points is consistently larger for real cities. There really does seem to be a property, peculiar to cities, that makes them harder to find your way around than other types of network.
...
As you might expect, Manhattan, with its chequered grid plan, proves easier to navigate than the three, less orderly Swedish cities considered (Stockholm, Malmö and Umea). But even Manhattan is more complex, by these measures, than the network formed by flights between US airports.


De två refererade papren är
Martin Rosvall, Ala Trusina, Petter Minnhagen, Kim Sneppen:
Networks and Cities: An Information Perspective
Abstract:
Traffic is constrained by the information involved in locating the receiver and the physical distance between sender and receiver. We here focus on the former, and investigate traffic in the perspective of information handling. We re-plot the road map of cities in terms of the information needed to locate specific addresses and create information city networks with roads mapped to nodes and intersections to links between nodes. These networks have the broad degree distribution found in many other complex networks. The mapping to an information city network makes it possible to quantify the information associated to locating specific addresses. We suggest a size-rescaled information measure that allows us to quantify the complexity in city organization and other complex networks.

Rui Carvalho, Alan Penn:
Scaling and universality in the micro-structure of urban space
Abstract
We present a broad, phenomenological picture of the distribution of the length of open space linear segments, l, derived from maps of 36 cities in 14 different countries. By scaling the Zipf plot of l, we obtain two master curves for a sample of cities, which are not a function of city size. We show that a third class of cities is not easily classifiable into these two universality classes. The cumulative distribution of l displays power-law tails with two distinct exponents, alphaB=2 and alphaR=3. We suggest a link between our data and the possibility of observing and modelling urban geometric structures using Lévy processes.

Se även
Complex Networks (Umeå Universitet)
NORDITA Network Research
Space Syntax.

Posted by hakank at 09:27 EM Posted to Social Network Analysis/Complex Networks | Comments (2)

augusti 07, 2004

Duncan Watts om 9/11-kommissionen

Duncan Watts kritiserar 9/11-kommissionens förslag i Slate-artikeln Decentralized Intelligence - What Toyota can teach the 9/11 commission about intelligence gathering .

The most publicized recommendation of the 9/11 commission—and one President Bush and Sen. John Kerry have raced to endorse—is that the United States create a national director of intelligence. Centralizing is an understandable response to the pre-9/11 intelligence fiasco. But as organizational science and history show, it's also a misguided one.

Watts menar att vi i stället för att skapa centralinstitutioner för att lösa denna typ av problem ska lära oss av organisationer som Toyota för att hantera krissituationer. T.ex. när ett helt lager med viktiga komponenter brann ner, så lyckades man lösa detta på tre dagar, men inte genom att skapa ett centralt organ som detaljstyrde hur allting skulle lösas.

Rather than relying on the guidance and coordination of an inspired leader (control mode), the response was a bewildering display of truly decentralized problem solving: More than 200 companies reorganized themselves and each other to develop at least six entirely different production processes, each using different tools, different engineering approaches, and different organizational arrangements. Virtually every aspect of the recovery effort had to be designed and executed on the fly, with engineers and managers sharing their successes and failures alike across departmental boundaries, and even between firms that in normal times would be direct competitors.

Artikeln ger fler exempel på denna typ av krislösningar. Det finns dock ingen patenlösning som är giltig för alla situationer.

So, how does one make this kind of magic happen? Unfortunately, no one is quite sure. Different organizations, from business firms to research communities to the military, have tried to address their collective problem-solving needs in a variety of ways. Some militaries make a point of training their officers in joint-service academies and staff colleges, both of which serve the purpose of building friendships and professional relationships across otherwise frosty institutional boundaries. Academic researchers, for their part, organize interdisciplinary conferences and working groups that serve to introduce disciplinary specialists who turn out to have complementary knowledge or skill sets, but who otherwise would never have had occasion to meet. And business firms from the automotive to high-tech and finance industries deliberately cross-pollinate their intellectual capital by fostering worker exchanges across divisions or even firms, building problem-solving teams around tasks rather than departments, emphasizing informal agreements and collaborations over formal contracts, and organizing sophisticated team-building exercises for geographically dispersed junior executives.


Watts skriver mer om decentraliserade nätverk (där bl.a. ovanstående exempel diskuteras mer i detalj) i sin fascinerande bok Six Degrees: The Science of a Connected Age. Fler böcker i ämnet nämns i Social Network Analysis och Complex Networks - En liten introduktion samt i bloggkategorin Social Network Analysis/Complex Networks.

Läs även Malcolm Gladwells Connecting the dots - The paradoxes of intelligence reform för en kritisk genomgång hur CIA och FBI förändrats beroende på vilka typer av kriser som nyss har uppstått.

Posted by hakank at 11:06 FM Posted to Social Network Analysis/Complex Networks | Comments (5)

juli 30, 2004

See you in the Funny Papers: Cartoons and Social Networks

Linton C. Freeman See you in the Funny Papers: Cartoons and Social Networks, ett roligt sätt att beskriva sociala nätverk.

From time to time a branch of science captures the imagination of the public; it gets "hot." When that happens, references to the "hot" item appear in newspapers, in novels, in movies -- even in cartoons. Forty odd years ago, for example, Ray Birdwhistell (1952) first introduced kinesics, the field concerned with the importance of non-verbal gestures in human communication. Very soon, Al Capp introduced a new character in his comic strip, Li'l Abner. Capp began a series of based on the activities of a "Professor Fleasong," a specialist in the study of "toe gestures."

The field of social network analysis seems to be in that kind of center-stage position today. The fact that social networks is "hot" is indicated by its increasingly frequent appearance in the popular media, particularly in the comics. And, interestingly enough, many of those treatments are quite sophisti-cated. They refer, not just to the network idea, but they often reflect some of the more subtle and sophisticated ideas from our field -- and they do it with wit.

Publicerad år 2000 i tidskriften CONNECTIONS, An official journal of International Network for Social Network Analysis. Rätt många nummer finns online.

(Via Online Business Networks.)

Posted by hakank at 05:47 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

juli 19, 2004

First Monday

Den senaste First Monday innehåller bland annat:

Hassan Masum and Yi–Cheng Zhang: Manifesto for the Reputation Society
Abstract:
Information overload, challenges of evaluating quality, and the opportunity to benefit from experiences of others have spurred the development of reputation systems. Most Internet sites which mediate between large numbers of people use some form of reputation mechanism: Slashdot, eBay, ePinions, Amazon, and Google all make use of collaborative filtering, recommender systems, or shared judgements of quality.

But we suggest the potential utility of reputation services is far greater, touching nearly every aspect of society. By leveraging our limited and local human judgement power with collective networked filtering, it is possible to promote an interconnected ecology of socially beneficial reputation systems — to restrain the baser side of human nature, while unleashing positive social changes and enabling the realization of ever higher goals.

Posted by hakank at 06:45 FM Posted to Social Network Analysis/Complex Networks | Comments (0)

juni 28, 2004

Network Logic

Samlingsboken Network Logic - Who governs in an interconnected world?, utgiven av Demos, innehåller papers om sociala och andra nätverk, och presenteras på följande sätt:

From the Internet to Al Qaeda, the teetering electricity grid to old school ties, we live in a world of networks. A profoundly disruptive shift has occurred in our societies, making networks the most important organisational form of our time and reshaping the activities of families, governments and businesses.

Our public response to these changes has so far been partial and fragmented. Although social, political and technological networks hold our modern world together, we lack the language to apply them to solving our common problems.

But if we can learn more accurately to understand the patterns and impacts of networks, we can begin to tap their full potential for organisation and decision-making, and to make possible new forms of coordination and collective action.

In this collection of essays, Demos seeks to address that challenge. Drawing on some of the world's leading thinkers on networks across a range of disciplines, we seek to distil the most important lessons from the study of networks and address some of the critical questions that our 'network society' presents: from the distribution of power and inequality to the future of civic participation and the impact of new technologies.

Embracing this network logic will help us to change not just our tools of intervention, but our ways of seeing the world.

Ett urval:

Boken finns att ladda ner som helhet eller delar via ovan nämnda sida.

Posted by hakank at 07:02 FM Posted to Social Network Analysis/Complex Networks | Comments (0)

juni 08, 2004

How Org Charts Lie

How Org Charts Lie är ett utdrag från boken The Hidden Power of Social Networks: Understanding How Work Really Gets Done in Organizations av Rob Cross och Andrew Parker.

The results of this organization's social network analysis are fairly typical. Even in small, contained groups, executives are often surprised by patterns of collaboration that are quite different from their beliefs and from the formal organization chart. Getting an accurate view of a network helps with managerial decision making and informs targeted efforts to promote effective collaboration. Rather than leave the inner workings of a network to chance, executives can leverage the insights of a social network analysis to address critical disconnects or rigidities in networks and create a sense-and-respond capability deep within the organization.

Se även
Organizational Network Analysis (som länkades till för någon månad sedan, dock under en något annorlunda titel).

Posted by hakank at 06:49 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

juni 04, 2004

SNA för R

Carter Butts har kommit med en ny version av SNA-paketet för R. Se vidare Carter's Archive of S Routines for the R Statistical Computing Environment. Paketet är nu uppe i version 0.44-1.

Se även CRAN-sidan för paketet.

Posted by hakank at 09:19 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

maj 27, 2004

Hjärnans lilla värld

New Scientist: Small world networks key to memory:

If you recall this sentence a few seconds from now, you can thank a simple network of neurons for the experience. That is the conclusions of researchers who have built a computer model that can reproduce an important aspect of short-term memory.
...
Now it looks as if working memory, which allows short-term recall of fleetingly remembered information such as phone numbers, relies on the same property [small world network]. This type of memory resides in an area at the front of the brain called the prefrontal cortex, which is involved in learning, planning and many higher cognitive functions.
...
The new work may be an important step towards a theory of how the brain works. "What I really like about this system is how simple it is," says John White, a biomedical engineer at Boston University. "That means it might be possible to move from computer models to a rigorous mathematical description, which would really advance the field."

Posted by hakank at 09:00 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

maj 24, 2004

Hur man får goda idéer

New York Times-artikeln Where to Get a Good Idea: Steal It Outside Your Group skriver om hur goda idéer kommer till. (Inte helt opassande läsning efter skrivande av ett långt mail till Peter Lindberg kring hans Om intellektuellt skapande, Lynchs "imageability", systemutveckling, m.m.).

Got a good idea? Now think for a moment where you got it. A sudden spark of inspiration? A memory? A dream?

Most likely, says Ronald S. Burt, a sociologist at the University of Chicago, it came from someone else who hadn't realized how to use it.

"The usual image of creativity is that it's some sort of genetic gift, some heroic act," Mr. Burt said. "But creativity is an import-export game. It's not a creation game."
...
"People who live in the intersection of social worlds," Mr. Burt writes, "are at higher risk of having good ideas."


Se även
Ronald S. Burt
Han har skrivit boken Structural Holes: The Social Structure of Competition som nämns i artikeln. (Boken har inköpts men ännu inte lästs.)

Structural Holes and Good Ideas (PDF) är en preprint funnen via google. Kanske av det paper som nämns i artikeln?

Posted by hakank at 09:20 EM Posted to Social Network Analysis/Complex Networks | Comments (9)

maj 14, 2004

Scale-Free Network Business Development Strategy

Tom Sato: Scale-Free Network Business Development Strategy (PDF)

Human society, Internet, interaction of protein, and the business community have one thing in common. They are all networks of nodes that interact with each other and the shape of these networks all have the same scale-free characteristics. Scale-free network has few hubs that connect vast numbers of nodes and a large number of nodes that has very few connections. You can spot it by plotting a graph of number of nodes verses number of links. Scale free always has a distribution that follows the power law. It is the network topology of choice because of its robustness, fast communication and ability to evolve.

This paper examines how to apply scale-free network in business development, and use it to grow the business into unbeatable success. It is based on the author’s experience as Windows Product Manager at Microsoft Japan during the Eighties and two ground breaking books, Linked by Prof. Albert-Laszlo Barabasi at Univ. of Notre Dame and Tipping Point by journalist Malcolm Gladwell.

Posted by hakank at 07:12 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

maj 03, 2004

BBC 4 program om small world (från förra året, men i alla fall)

Råkade just hitta BBC Radio 4-programmet Small World från 30 juli 2003, som de första 15 minuterna handlar om small worlds-hypotesen, dvs Stanley Milgrams experiment kring Six Degrees of Separation och den senare utvecklingen av denna teori, såsom komplexa nätverk etc. Man pratar även om Harry Potter och andra spridnings-/påverkanfenomen. Intervjuad blir en av experterna inom området Duncan Watts.

Faktiskt nämns inte bara Milgrams Six Degrees-experiment utan även andra. Hmm, det är nog snart dags att börja läsa Milgram-biografin som har legat bläddrat men annars orörd ett tag.

Se även
Social Network Analysis och Complex Networks - En liten introduktion samt blogganteckningarna inom denna kategori, t.ex. Recension av Malcolm Gladwell "The Tipping Point".
En kort notis: Stanley Milgram.

Posted by hakank at 07:10 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

Politiska köpmönster på webben: Divided we stand - take III

Valdis Krebs, namnkunnig social nätverksanalyst, har tidigare skrivit om köpmönster vad gäller politiska böcker på Amazon, som visar klustring i vänster- respektive högerböcker (eller vilken dimension man nu vill se detta).

I den nya tredje analysen Political Patterns on the WWW: Divided We Stand... Less skrivs bland annat:

Many thought that Woodward's latest book, Plan of Attack would be read equally by pro and anti-Bush readers. The 'also bought' data does not support that theory. Woodward's book is being bought mostly by those reading left leaning books.

The big difference between this network map and the previous two are the number of books in the middle. The release of two popular middle books, colored purple, exposed a network of middle books. Ghost Wars reveals one group of middle books, while The Rise of the Vulcans reveals a second group. There are now more bridges from right to left [and back] than in the previous maps.

Yet, the division between left and right remains strong. Our network metrics, as well as the visuals, show two obvious clusters with high preference for homogeneous choices. Echo chambers of right and left thought still remain in America.

De två tidigare analyserna: Divided We Stand??? samt Divided We Stand... Still.

Läs gärna även The Social Life of Books Visualizing Communities of Interest via Purchase Patterns on the WWW.

Posted by hakank at 06:18 EM Posted to Social Network Analysis/Complex Networks | Comments (0)

maj 02, 2004

Jazz-nätverk

Douglas Heckathorn, Joan Jeffri:
Jazz Networks: Using Respondent-Driven Sampling to Study Stratification in two Jazz Musician Communities (PDF).

Abstract:
The literature on jazz has focused on biographies of major figures, the history of styles, and the influence of jazz on society. Only two studies, one in the Netherlands and one in France, have included obscure musicians as well as the famous, and both were limited by the use of nonprobability sampling methods. This study is based on 564 interviews with jazz musicians in the greater New York metropolitan area and the San Francisco Bay area. It employs respondent-driven sampling, a method that permits representative samples to be drawn from hard-to-reach populations. The analysis extends that method by introducing a means for studying the structure of large social networks, by identifying combinations of in-group affiliation bias (homophily) and out-group affiliation bias (heterophily). The results indicate that cohesion among jazz musicians is based, in part, on race and ethnicity, gender, and age (the latter two of which can also be the basis for stratification), and on style of performance, but the most important determinants are professional contacts, involvement in the jazz community, and primary instrument. Inequality by age and gender are greater in San Francisco, and racial and ethnic boundaries are stronger in New York. Drawing on concepts from the literature on small-world networks, we examine spatial networks, and San Francisco is found to have stronger small-world properties than New York.



Conclusion: Is the Jazz Musician Community a Small World?
....
Our study also has practical significance. It shows that the boundaries of the jazz musician community can be precisely determined, and therefore programs designed to foster the development of this art form can be precisely targeted and their effects documented. Reliable and consistent data about jazz musicians and their needs provide a useful guide to appropriate amounts of funding for agents, advocates, and the artists themselves.
...
We conclude, first, that both the NYC and the SF jazz musician communities qualify as small-world systems: both have far more than the rather modest number of long-distance ties now recognized as required to endow a network with small-world properties. Our second conclusion is that geographic integration is greater in SF, making San Francisco the smaller world. 30


Se även
'Small world' becomes a scientific sampling tactic
Respondent Driven Sampling
How Many Jazz Musicians Are There?
Joan Jeffri: Changing the beat: A study of the Worklife of Jazz Musicians, Executive Summary (PDF)
Joan Jeffri: Changing the beat: A study of the Worklife of Jazz Musicians, Survey Results (PDF)

Ett paper som refereras i flera av ovanstående dokument är Douglas Heckathorn, Joan Jeffri: Finding the beat: Using respondent-driven sampling to study jazz musicians, publicerad i Poetics 28 (4) 2001, tyvärr ej tillgängligt å nätet.

Posted by hakank at 08:17 FM Posted to Social Network Analysis/Complex Networks | Comments (0)