SBU CSE 591 - Social Networks Vis (7 pages)

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Social Networks Vis



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Overview Social Networks Vis Supriya Garg Presentation for CSE591 3rd May 2007 Measures in SNA What are social networks A social network is a social structure made of nodes that are tied by one or more specific types of relations such as financial exchange friends kinship airline routes etc The nodes are generally individuals or organizations Social network analysis SNA has emerged as a key technique in modern sociology anthropology sociolinguistics geography social psychology information science and organizational studies What are social networks Key concepts in social networks Growth of social networks visualization Techniques used in social networks visualization Alternatives to the traditional methods Some applications Vizster Flink Betweenness The extent to which a node is directly connected only to those other nodes that are not directly connected to each other Centrality Closeness The degree an individual is near all other individuals in a network It is the inverse of the sum of the shortest distances between each individual and every other person in the network Centrality Degree Its simply the degree of the node Flow betweenness Centrality The degree that a node contributes to sum of maximum flow between all pairs of nodes not that node Centrality Eigenvector It is a measure of the importance of a node in a network It assigns relative scores to all nodes in the network based on the principle that connections to nodes having a high score contribute more to the score of the node in question Measures in SNA cont Social Network Vis Centralization The difference between the n of links for each node divided by maximum possible sum of differences Clustering Coefficient The clustering coefficient is a In his early works Moreno 1934 introduced five important ideas about the proper construction of images of social networks measure of the likelihood that two associates of a node are associates themselves Structural Equivalence Refers to the extent to which actors have a common set of linkages to other actors in the system The actors don t need to have any ties to each other to be structurally equivalent Radiality Degree an individual s network reaches out into the network and provides novel information and influence Reach The degree any member of a network can reach other members of the network Draw graphs Draw directed graphs Use colors to draw multigraphs Vary the shapes of points to communicate characteristics of social actors Variations in the locations of points can be used to stress important structural features of the data The last idea is used frequently by rural sociologists and geographers Lady bountiful Lundberg Steele Moreno s ideas illustrated Boys Girls Friendship Choices among 4th graders Positive and Negative Choices in a Football Team One structural feature that was of great interest to early investigators was the sociometric status of each point The sociometric status of a point was defined as the number of choices or the strength of the choices received by that point Lundberg and Steele 1938 for example specified the nuclei of a network as those actors with high sociometric status They constructed their famous lady bountiful image by making the nuclei larger than other points and by placing them near the middle of their drawing Original Computer based 3 D rendering Line Images Grounded in Computation Evolution of ways of representation Matrix of links between corporations and corporate directors 55 X 55 matrix to a 3D array using Multi Dimensional Scaling MDS Factor analysis of the correlation matrix in this case 16 correlations Individual and corporate proximities Interactive images in the era of web browsers Representation as a Galois Lattice One way is to use java applets A second browser based way of handling images is provided by VRML Virtual Reality Modeling Language composite c square s even e odd o prime p Here lattice means an order To create it the matrix is taken as an input and the natural object clusters and natural property clusters are deduced This image is a 3 D representation of data on friendship ties collected at a residential college at an Australian university Force directed algorithms A graph layout scheme used in social networks vis Force directed algorithms are a class of algorithms for drawing graphs in an aesthetically pleasing way Their purpose is to position the nodes of a graph so that all the edges are of more or less equal length and there are as few crossing edges as possible They achieve this by assigning forces amongst the set of edges and the set of nodes the most straightforward method is to assign forces as if the edges were springs and the nodes were electrically charged particles The forces are applied to the nodes pulling them closer together or pushing them further apart This is repeated iteratively until the system comes to an equilibrium state i e their relative positions do not change anymore from one iteration to the next Connectivity Well known graph Going beyond the graph Alternative representations have mostly been used to augment the node link graphs Histograms Treemaps Etc Treemaps as a Tool for Social Network Analysis From FLINK The who is who of the Semantic Web Node Degrees by Year Month 2001 Node Degrees by Month The ENRON dataset PostHistory interface with calendar Tree Maps PostHistory is a visualization that focuses on time and rhythm where the variations in long term email exchange are revealed to the user 1 Left panel a Size of square traffic b Color of square directedness 2 Right panel vertical circular version a At the top centre ego b Most frequent contacts closer to the ego Oct 2001 Node Degrees by Name Oct 2001 Node Degrees by Title Name The ENRON dataset Vizster Vizster is an interactive visualization tool for online social networks allowing exploration of the community structure of social networking services such as friendster com tribe net and orkut The networks are presented as egocentric networks networks consisting of an individual and their immediate friends Users can expand the display by selecting nodes to make visible others immediate friends as well In pursuing this design they chose to violate Shneiderman s mantra of overview first zoom and filter then details on demand instead opting for a philosophy of start with what you know then grow Vizster Visualized search results for the query student Focus Context view by inflating highlighted nodes Vizster Community structure Community


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