Additional Core/Peripheral Classification Methods

[Leo-Send]

Prerequisites

• I adhere to the coding conventions (described here) in my code.
• I have updated the copyright headers of the files I have modified.
• I have written appropriate commit messages, i.e., I have recorded the goal, the need, the needed changes, and the location of my code modifications for each commit. This includes also, e.g., referencing to relevant issues.
• I have put signed-off tags in all commits.
• I have updated the changelog file NEWS.md appropriately.
• I have checked whether I need to adjust the showcase file showcase.R with respect to my changes.
• The pull request is opened against the branch dev.

Description

Add four new metric which can be used for the classification of authors into core and peripheral:
Betweenness, which measures the number of shortest paths between developers that go through a given developer vertex;
Closeness, which measures how close a developer is to all others by taking the inverse of the sum of all of it's shortest paths;
Pagerank, which is based on Google's Pagerank algorithm, which is closely related to Eigenvector Centrality;
Eccentricity, which measures the distance to the furthest developer vertex.

Changelog

Added

• Add four new metric that can be used for the classification of authors into core and peripheral: betweenness, closeness, pagerank, and eccentricity (PR Additional Core/Peripheral Classification Methods #276, e27acb5, 2178808)

Changed/Improved

• Include core/peripheral classification in the README.md (PR Additional Core/Peripheral Classification Methods #276, 6101e11, c6744c0, 5fc2da5)

[bockthom]

I had a quick look at the implementation (but not yet at the tests).
Please find my initial comments below.

[bockthom]

I've had a quick look at your additions to the README, see my detailed comments below.

[bockthom]

As I haven't had a look at the tests yet, I have now done so. I only have a few minor comments (but I did not check the actual centrality values; especially for eccentricity, I still don't have an impression whether the values do make sense or not 🙈)

In addition to my comments below, please don't forget about the changes to the README regarding "author networks" that we have agreed on in today's meeting.

[bockthom]

Just two comments regarding wording:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.67%. Comparing base (b018a43) to head (c70a0bb).
Report is 16 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #276      +/-   ##
==========================================
+ Coverage   81.13%   81.67%   +0.54%     
==========================================
  Files          16       16              
  Lines        5105     5147      +42     
==========================================
+ Hits         4142     4204      +62     
+ Misses        963      943      -20     

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[hechtlC]

First of all thank you for the enhancement @Leo-Send!
I have just found some small typos and wording issues. Once these are fixed, we can merge this PR.