The visualization of the lobby network.

<p>The organizations of different types are marked in different colors as follows, red: companies; pink: trade, bussiness & professional associations; cyan: professional consultants and law firms; blue: NGOs; green: think tanks and research institutions. The size of the node is proportional to the number of lobbyists of the organization.</p

Information Filtering via Heterogeneous Diffusion in Online Bipartite Networks

<div><p>The rapid expansion of Internet brings us overwhelming online information, which is impossible for an individual to go through all of it. Therefore, recommender systems were created to help people dig through this abundance of information. In networks composed by users and objects, recommender algorithms based on diffusion have been proven to be one of the best performing methods. Previous works considered the diffusion process from user to object, and from object to user to be equivalent. We show in this work that it is not the case and we improve the quality of the recommendation by taking into account the asymmetrical nature of this process. We apply this idea to modify the state-of-the-art recommendation methods. The simulation results show that the new methods can outperform these existing methods in both recommendation accuracy and diversity. Finally, this modification is checked to be able to improve the recommendation in a realistic case.</p></div

The basic statistical properties of each layer of the lobby network.

<p><i>N</i> is the number of nonisolated nodes. <i>E</i> is the number of links. 〈<i>k</i>〉 is the average degree of the network. <i>H</i> is the reciprocal of the Herfindahl index of the degree sequence. <i>d</i> is the average shortest path length of the network. <i>c</i> is the average clustering coefficient of the network. <i>r</i> is the assortativity coefficient of the network. We consider these networks as undirected when calculating these indices.</p

The number of links within each group in the empirical networks (i.e. <i>links</i>) and the randomly reshuffled networks (i.e. <i>links</i>*).

<p>The number of links within each group in the empirical networks (i.e. <i>links</i>) and the randomly reshuffled networks (i.e. <i>links</i>*).</p

The number of links within and between domains in the empirical networks (i.e. <i>links</i>) and the randomly reshuffled networks (i.e. <i>links</i>*).

<p>In the affiliation network, <i>i</i> → <i>j</i> means <i>i</i> is affiliated to <i>j</i>. In the sharesholding network, <i>i</i> → <i>j</i> means <i>i</i> is holding share of <i>j</i>. The interlock network is an undirected network, <i>i</i> → <i>j</i> means the number of common managers between <i>i</i> and <i>j</i>.</p

The degree distribution of users and objects in (a) Movielens, (b) Netflix and (c) RYM networks. (d), (e) and (f) are <i>d</i>(<i>k</i>) vs <i>k</i> in Movielens, Netflix and RYM networks, respectively.

<p>For the blue curve, <i>k</i> denotes the degree of users and <i>d</i>(<i>k</i>) denotes the average degree of the neighboring objects of these users. For the red curve, <i>k</i> denotes the degree of objects and <i>d</i>(<i>k</i>) denotes the average degree of the neighboring users of these objects.</p

The (a) Ranking score, (b) Precision, (c) personlization and (d) novelty of the H-Hybrid method in parameter space (λ₁, λ₂) in Netflix network.

<p>The dashed line marks the region where RS is better than the RS value achievable with O-Hybrid method.</p

λ2* vs λ₁ in (a) Movielens, (b) Netflix and (c) RYM data.

<p>The line corresponding to λ₁ = λ₂ is plotted to guide eyes. In (d)(e)(f), the minimum <i>RS</i>* is obtained for </p><p></p><p></p><p></p><p><mi>λ</mi><mn>2</mn><mo>*</mo></p><p></p><p></p><p></p> of the upper panels.<p></p

The results of all the metrics for the O-Hybrid and H-Hybrid algorithms under the three-fold data division.

<p>The entries corresponding to the best performance over all methods are emphasized in black.</p

The correlation of <i>dr</i> with <i>r</i>_<i>k</i> for top 100 objects in the real future.

<p>Black lines with circles present the result of TBP with the best parameter <i>γ</i>*, red lines with triangles present the result of PBP with the best parameter <i>λ</i>*, and blue lines with diamonds present the result of TBP with <i>γ</i> = 1. <i>T</i>_<i>F</i> is set as 30 days for all data sets.</p