Definitions, network representations, program Pajek

1. Network
   • definition
   • representation (matrix, graph)
2. Types of networks
   • undirected networks
   • directed networks
   • mixed networks
   • 2-mode networks
3. Size and density
   • small and large networks
   • sparse and dense networks
   • network density
4. Program Pajek
   • description of networks in input file
   • arcs, edges
   • arcslist, edgeslist
   • matrix
   • other formats
   • interactive definition of networks
   • network layouts
     • automatic drawing
     • manual drawing

   Examples

   1. Definition of networks in input file, interactive definitions of selected network, getting layouts in program Pajek.

   Assignment

   1. Each student gets his/her own network. Detailed instructions to complete the first assignment:
      Enter the network in Pajek NET format. In network there should be only arcs, there are NO edges. Bidirectional arcs SHOULD NOT be transformed to edges!
      Write the question that generates your network. Draw the network nicely using automatic and manual drawing. Include the picture in the report. Find out the total number of arcs and the density of the network.
      Interprete the results: using layout only try to find basic characteristics of the network: who are the most important (central) students? Are there any groups of densely connected students? Isolated students? Are there any differences according to gender? Etc.
      Later, during the course, we will be able to compute all these characteristics, and at that time we will check if our conclusions obtained from the layout only were correct or not (sometimes the picture can be misleading). Additionally to printed report next week students should bring their NET files as well. NET files should be named according to their surnames (e.g. Smith.net). Professor will use that file to check if the network was entered correctly and if results computed in all assignments are correct.

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   Slides (PDF)
   Test networks (ZIP)