Coverage.cs

using System;
using System.Collections.Generic;
using System.Linq;
using MNCD.Core;

namespace MNCD.Evaluation.SingleLayer
{
    /// <summary>
    /// Coverage
    /// Based on:
    /// Community detection in graphs
    /// https://arxiv.org/abs/0906.0612
    /// Santo Fortunato.
    /// </summary>
    public static class Coverage
    {
        /// <summary>
        /// Computes coverage for partition, the ratio of the number of intra-community
        /// edges by the total number of edges.
        /// </summary>
        /// <param name="network">
        /// Network that is partitioned.
        /// </param>
        /// <param name="communities">
        /// List of communities for which the coverage should be computed.
        /// </param>
        /// <returns>
        /// The ratio of the number of intra-community edges by the total number of edges.
        /// </returns>
        public static double Get(Network network, List<Community> communities)
        {
            if (network.LayerCount != 1)
            {
                throw new ArgumentException("Coverage only works on single layer networks.");
            }

            var intra = GetIntraEdges(network, communities);
            var total = GetTotalEdges(network);

            if (total > 0)
            {
                return intra / (double)total;
            }
            else
            {
                return 1.0;
            }
        }

        private static int GetIntraEdges(Network network, List<Community> communities)
        {
            var count = 0;
            foreach (var edge in network.Layers.First().Edges)
            {
                if (communities.Any(c => c.Actors.Contains(edge.From) && c.Actors.Contains(edge.To)))
                {
                    count++;
                }
            }

            return count;
        }

        private static int GetTotalEdges(Network network)
        {
            return network.Layers.First().Edges.Count;
        }
    }
}