2 Emails in HP Six degrees or six

Όψεις (2) Emails in HP

Six degrees or six Worlds Instant messenger Erdos number (4 -5) Bacon number (2. 9)

Network Datasets • • Collaboration graphs Who-talks-to-whom graph Information graphs Who-transacts-to-whom Technological linking Biological linking Natural world ………….

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GEPHI • • • https: //gephi. github. io/ Start Gephi Δημιουργία απλού γράφου Center on graph, enlarge Edit node (? Tools) Dining table partners Force atlas 2 Reset colors, reset size (right click) Show node labels, size

Δομές Δεδομένων • Edges partition (choice) apply • Data laboratory • Preview

Node metrics

Degree distribution

Components

Gephi (dining table…) • • • Ranking nodes indegree size (spline) Compute average degree (statistics δεξιά) Data laboratory – nodes sort Statistics connected components. . Partition nodes strongly connected

Centrality • http: //moviegalaxies. com/ indegree outdegree To Χ έχει σημαντικότερη θέση από το Y betweenness closeness

Αριθμοί normalization divide degree by the max. possible, i. e. (N-1)

real-world examples example financial trading networks high in-centralization: one node buying from many others low in-centralization: buying is more evenly distributed

Κι άλλο παράδειγμα A B C D E n A lies between no two other vertices n B lies between A and 3 other vertices: C, D, and E n C lies between 4 pairs of vertices (A, D), (A, E), (B, D), (B, E) n note that there are no alternate paths for these pairs to take, so C gets full credit

Quiz: Find a node that has high betweenness but low degree

Quiz Q: Find a node that has low betweenness but high degree

Partitioning • Components • Κλίκες • Άλλα (cores – k-cores – clans, …)

Kάλυψη • Spanning tree Initialize: Vnew = {x}, where x is an arbitrary node (starting point) from V, Enew = {} Repeat until Vnew = V: Choose an edge (u, v) with minimal weight such that u is in Vnew and v is not (if there are multiple edges with the same weight, any of them may be picked) Add v to Vnew, and (u, v) to Enew Output: Vnew and Enew describe a minimal spanning tree