Université de Fribourg

Study of market model describing the contrary behaviors of informed and uninformed agents: Being minority and being majority

Zhang, Yu-Xia ; Liao, Hao ; Medo, Matúš ; Shang, Ming-Sheng ; Yeung, Chi Ho

In: Physica A: Statistical Mechanics and its Applications, 2016, vol. 450, p. 486–496

In this paper we analyze the contrary behaviors of the informed investors and uniformed investors, and then construct a competition model with two groups of agents, namely agents who intend to stay in minority and those who intend to stay in majority. We find two kinds of competitions, inter- and intra-groups. The model shows periodic fluctuation feature. The average distribution of...

Université de Fribourg

Recommender systems

Lü, Linyuan ; Medo, Matúš ; Yeung, Chi Ho ; Zhang, Yi-Cheng ; Zhang, Zi-Ke ; Zhou, Tao

In: Physics Reports, 2012, vol. 519, no. 1, p. 1–49

The ongoing rapid expansion of the Internet greatly increases the necessity of effective recommender systems for filtering the abundant information. Extensive research for recommender systems is conducted by a broad range of communities including social and computer scientists, physicists, and interdisciplinary researchers. Despite substantial theoretical and practical achievements, unification...

Université de Fribourg

Enhancing topology adaptation in information-sharing social networks

Cimini, Giulio ; Chen, Duanbing ; Medo, Matúš ; Lü, Linyuan ; Zhang, Yi-Cheng ; Zhou, Tao

In: Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 2012, vol. 85, no. 4, p. 046108

The advent of the Internet and World Wide Web has led to unprecedent growth of the information available. People usually face the information overload by following a limited number of sources which best fit their interests. It has thus become important to address issues like who gets followed and how to allow people to discover new and better information sources. In this paper we conduct an...

Université de Fribourg

Heterogeneity, quality, and reputation in an adaptive recommendation model

Cimini, Giulio ; Medo, Matúš ; Zhou, Tao ; Wei, Dong ; Zhang, Yi-Cheng

In: The European Physical Journal B - Condensed Matter and Complex Systems, 2011, vol. 80, no. 2, p. 201-208

Recommender systems help people cope with the problem of information overload. A recently proposed adaptive news recommender model [M. Medo, Y.-C. Zhang, T. Zhou, Europhys. Lett. 88, 38005 (2009)] is based on epidemic-like spreading of news in a social network. By means of agent-based simulations we study a “good get richer” feature of the model and determine which attributes are...

Université de Fribourg

Emergence of scale-free leadership structure in social recommender systems

Zhou, Tao ; Medo, Matúš ; Cimini, Giulio ; Zhang, Zi-Ke ; Zhang, Yi-Cheng

In: PLoS ONE, 2011, vol. 6, no. 7, p. e20648

The study of the organization of social networks is important for the understanding of opinion formation, rumor spreading, and the emergence of trends and fashion. This paper reports empirical analysis of networks extracted from four leading sites with social functionality (Delicious, Flickr, Twitter and YouTube) and shows that they all display a scale-free leadership structure. To reproduce this...

Université de Fribourg

Solving the apparent diversity-accuracy dilemma of recommender systems

Zhou, Tao ; Kuscsik, Zoltán ; Liu, Jian-Guo ; Medo, Matúš ; Wakeling, Joseph Rushton ; Zhang, Yi-Cheng

In: Proceedings of the National Academy of Sciences of the USA - PNAS, 2010, vol. 107, no. 10, p. 4511-4515

Recommender systems use data on past user preferences to predict possible future likes and interests. A key challenge is that while the most useful individual recommendations are to be found among diverse niche objects, the most reliably accurate results are obtained by methods that recommend objects based on user or object similarity. In this paper we introduce a new algorithm specifically to...

Université de Fribourg

Adaptive model for recommendation of news

Medo, Matúš ; Zhang, Yi-Cheng ; Zhou, Tao

In: Europhysics Letters, 2009, vol. 88, no. 3, p. 38005

Most news recommender systems try to identify users' interests and news' attributes and use them to obtain recommendations. Here we propose an adaptive model which combines similarities in users' rating patterns with epidemic-like spreading of news on an evolving network. We study the model by computer agent-based simulations, measure its performance and discuss its robustness against bias and...

Université de Fribourg

Recommendation model based on opinion diffusion

Zhang, Yi-Cheng ; Medo, Matúš ; Ren, Jie ; Zhou, Tao ; Li, T. ; Yang, F.

In: Europhysics Letters, 2007, vol. 80, no. 6, p. 68003

Information overload in the modern society calls for highly efficient recommendation algorithms. In this letter we present a novel diffusion-based recommendation model, with users' ratings built into a transition matrix. To speed up computation we introduce a Green function method. The numerical tests on a benchmark database show that our prediction is superior to the standard recommendation...

Université de Fribourg

Bipartite network projection and personal recommendation

Zhou, Tao ; Ren, Jie ; Medo, Matúš ; Zhang, Yi-Cheng

In: Physical Review E, 2007, vol. 76, no. 4, p. 046115

One-mode projecting is extensively used to compress bipartite networks. Since one-mode projection is always less informative than the bipartite representation, a proper weighting method is required to better retain the original information. In this article, inspired by the network-based resource-allocation dynamics, we raise a weighting method which can be directly applied in extracting the...