dimitris kalamaras

mathematics, social network analysis, free software…

Author: Dimitris Kalamaras (Page 2 of 12)

SocNetV v1.7 brings Group Node Edit, new Properties dialog, file Previewer and more

A new SocNetV release hit the road today. Version 1.7 solves a number of bugs and brings lots of interesting and useful new features to our users. Binaries for Windows, Mac and Linux are already available in the project’s Downloads page. Here’s what’s new…

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SocNetV v1.6 released – a nice web crawler included!

The Social Network Visualizer project has just released its latest version 1.6. This new version brings back the web crawler feature, which has been disabled in the 1.x series so far, but in a much more improved form.

To start the web crawler, go to menu Network > Web Crawler or press Shift+C…

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An apache monitoring script

One of the daily routines administrators do is to monitor their web server logs for various interesting things: response codes (i.e. 500), attempts to access restricted pages, user-agents, ips, popular pages, even image hotlinking from other sites. In Linux servers, this can be easily done through shell one-liners involving various tools (tail, awk, sort, cut etc). Here is a bash script I use which automates apache monitoring for a given website.

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SocNetV and online social networks

When I started developing SocNetV back in 2005 the term “social network” had a simple sociological meaning; any group of somehow “connected” actors, which might interest a sociologist to study and analyse in terms of their social properties and patterns (centralities, triads, etc). The actors can be of any type (humans, animals, organisations, companies etc) and so the cause of them being connected: working in the same place, belong to the same hive/group, mentioning each other, having commercial relations etc. Thus the main reason behind developing SocNetV was to create a simple “point and click” application that would enable the researcher to load his real-life gathered data and visualize/analyze the network properties. Or, in case the network was small enough, perhaps recreate it with some clicks on a canvas before analysing it. Back then it had never occurred to me that the same “social network” would be used now-days to describe online communities of million of users. As a matter of fact, I always thought that this strand of sociology is more meaningful in analysing relatively small groups rather than thousands of interconnected actors. Nevertheless, the term is used now this way too and this means that Social Network Analysis software such as SocNetV face a new problem: people not knowing anything about Social Network Analysis as a hybrid sociology-mathematics discipline think that all the software does is to “automatically” analyse any given online virtual community; who is connected to whom and how. Which is certainly not true.

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Git: Which hours you commit the most

If you use Git for version controlling some projects of yours and you are a number-crunch fanboy, you might be interested to know which hours you (or some fellows in your team) are active the most. I mean which hours during the day you do your commits. This is onliner will do this for you. Run it from inside your project dir:

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Network analysis of national soccer teams in FIFA World Cup 2014

This is the abstract of a paper published in the International Journal of Performance Analysis in Sport (Vol.15, No.1). In the paper we analyzed the network characteristics of successful and unsuccessful national teams that participated in FIFA World Cup 2014.

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How to setup Maildir style virtual mailboxes in Debian with Postfix

Virtual mailboxes is a clear choice if you want to setup your mail server with multiple domains and non-Linux accounts. Of course, there are other and easier ways to setup Postfix for hosting multiple domains.

The most simple is to host additional (shared) domains by adding them to the ‘mydestination’ variable in postfix’s main.cf. But that solution lacks distinction between canonical and hosted domains ([email protected] is delivered to the same unix account as [email protected]).

A better approach is through “virtual aliases”, which allow separate domains and email addresses. For that, you only need to configure two parameters: ‘virtual_alias_domains = domain1.com domain2.com’ and ‘virtual_alias_maps = hash:/etc/postfix/virtual’. You declare the list of your hosted domains in the first and alias each one to a local linux account with the second (i.e. in /etc/postfix/virtual add “[email protected] root” to have mails sent to domain1.com’s postmaster delivered to root). However, this is not an optimal solution if you plan to host more and more domains or if you just don’t want to give shell access to your server.

The really best solution is to use the Postfix virtual mailbox delivery agent. With this approach, every email address has its own virtual mailbox and you need to setup only one system account (to be the owner of all mailboxes). And each domain’s mailboxes are properly arranged in the file system under the home dir of the owner account:


In this how-to, I describe the process that I followed to setup virtual mailboxes in my postfix server for a pet project of mine.

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