arXiv subjects

Eduardo Graells-Garrido

Publications and source records attributed to Eduardo Graells-Garrido.

31 records · Page 2Linked to original sources

arXiv2016

A Day of Your Days: Estimating Individual Daily Journeys Using Mobile Data to Understand Urban Flow

Nowadays, travel surveys provide rich information about urban mobility and commuting patterns. But, at the same time, they have drawbacks: they are static pictures of a dynamic phenomena, are expensive to make, and take prolonged periods of time to finish. However, the availability of mobile usage data (Call Detail Records) makes the study of urban mobility possible at levels not known before. This has been done in the past with good results--mobile data makes possible to find and understand aggregated mobility patterns. In this paper, we propose to analyze mobile data at individual level by estimating daily journeys, and use those journeys to build Origin-Destiny matrices to understand urban flow. We evaluate this approach with large anonymized CDRs from Santiago, Chile, and find that our method has a high correlation ($ρ= 0.89$) with the current travel survey, and that it captures external anomalies in daily travel patterns, making our method suitable for inclusion into urban computing applications.

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arXiv2016

Sentiment Visualisation Widgets for Exploratory Search

This paper proposes the usage of \emph{visualisation widgets} for exploratory search with \emph{sentiment} as a facet. Starting from specific design goals for depiction of ambivalence in sentiment, two visualization widgets were implemented: \emph{scatter plot} and \emph{parallel coordinates}. Those widgets were evaluated against a text baseline in a small-scale usability study with exploratory tasks using Wikipedia as dataset. The study results indicate that users spend more time browsing with scatter plots in a positive way. A post-hoc analysis of individual differences in behavior revealed that when considering two types of users, \emph{explorers} and \emph{achievers}, engagement with scatter plots is positive and significantly greater \textit{when users are explorers}. We discuss the implications of these findings for sentiment-based exploratory search and personalised user interfaces.

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arXiv2016

Data Portraits and Intermediary Topics: Encouraging Exploration of Politically Diverse Profiles

In micro-blogging platforms, people connect and interact with others. However, due to cognitive biases, they tend to interact with like-minded people and read agreeable information only. Many efforts to make people connect with those who think differently have not worked well. In this paper, we hypothesize, first, that previous approaches have not worked because they have been direct -- they have tried to explicitly connect people with those having opposing views on sensitive issues. Second, that neither recommendation or presentation of information by themselves are enough to encourage behavioral change. We propose a platform that mixes a recommender algorithm and a visualization-based user interface to explore recommendations. It recommends politically diverse profiles in terms of distance of latent topics, and displays those recommendations in a visual representation of each user's personal content. We performed an "in the wild" evaluation of this platform, and found that people explored more recommendations when using a biased algorithm instead of ours. In line with our hypothesis, we also found that the mixture of our recommender algorithm and our user interface, allowed politically interested users to exhibit an unbiased exploration of the recommended profiles. Finally, our results contribute insights in two aspects: first, which individual differences are important when designing platforms aimed at behavioral change; and second, which algorithms and user interfaces should be mixed to help users avoid cognitive mechanisms that lead to biased behavior.

cs.HC↗

arXiv2015

Encouraging Diversity- and Representation-Awareness in Geographically Centralized Content

In centralized countries, not only population, media and economic power are concentrated, but people give more attention to central locations. While this is not inherently bad, this behavior extends to micro-blogging platforms: central locations get more attention in terms of information flow. In this paper we study the effects of an information filtering algorithm that decentralizes content in such platforms. Particularly, we find that users from non-central locations were not able to identify the geographical diversity on timelines generated by the algorithm, which were diverse by construction. To make users see the inherent diversity, we define a design rationale to approach this problem, focused on an already known visualization technique: treemaps. Using interaction data from an "in the wild" deployment of our proposed system, we find that, even though there are effects of centralization in exploratory user behavior, the treemap was able to make users see the inherent geographical diversity of timelines, and engage with user generated content. With these results in mind, we propose practical actions for micro-blogging platforms to account for the differences and biased behavior induced by centralization.

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arXiv2015

Finding Intermediary Topics Between People of Opposing Views: A Case Study

In micro-blogging platforms, people can connect with others and have conversations on a wide variety of topics. However, because of homophily and selective exposure, users tend to connect with like-minded people and only read agreeable information. Motivated by this scenario, in this paper we study the diversity of intermediary topics, which are latent topics estimated from user generated content. These topics can be used as features in recommender systems aimed at introducing people of diverse political viewpoints. We conducted a case study on Twitter, considering the debate about a sensitive issue in Chile, where we quantified homophilic behavior in terms of political discussion and then we evaluated the diversity of intermediary topics in terms of political stances of users.

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arXiv2015

First Women, Second Sex: Gender Bias in Wikipedia

Contributing to history has never been as easy as it is today. Anyone with access to the Web is able to play a part on Wikipedia, an open and free encyclopedia. Wikipedia, available in many languages, is one of the most visited websites in the world and arguably one of the primary sources of knowledge on the Web. However, not everyone is contributing to Wikipedia from a diversity point of view; several groups are severely underrepresented. One of those groups is women, who make up approximately 16% of the current contributor community, meaning that most of the content is written by men. In addition, although there are specific guidelines of verifiability, notability, and neutral point of view that must be adhered by Wikipedia content, these guidelines are supervised and enforced by men. In this paper, we propose that gender bias is not about participation and representation only, but also about characterization of women. We approach the analysis of gender bias by defining a methodology for comparing the characterizations of men and women in biographies in three aspects: meta-data, language, and network structure. Our results show that, indeed, there are differences in characterization and structure. Some of these differences are reflected from the off-line world documented by Wikipedia, but other differences can be attributed to gender bias in Wikipedia content. We contextualize these differences in feminist theory and discuss their implications for Wikipedia policy.

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arXiv2015

Language, Twitter and Academic Conferences

Using Twitter during academic conferences is a way of engaging and connecting an audience inherently multicultural by the nature of scientific collaboration. English is expected to be the lingua franca bridging the communication and integration between native speakers of different mother tongues. However, little research has been done to support this assumption. In this paper we analyzed how integrated language communities are by analyzing the scholars' tweets used in 26 Computer Science conferences over a time span of five years. We found that although English is the most popular language used to tweet during conferences, a significant proportion of people also tweet in other languages. In addition, people who tweet solely in English interact mostly within the same group (English monolinguals), while people who speak other languages tend to show a more diverse interaction with other lingua groups. Finally, we also found that the people who interact with other Twitter users show a more diverse language distribution, while people who do not interact mostly post tweets in a single language. These results suggest a relation between the number of languages a user speaks, which can affect the interaction dynamics of online communities.

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arXiv2013

Data Portraits: Connecting People of Opposing Views

Social networks allow people to connect with each other and have conversations on a wide variety of topics. However, users tend to connect with like-minded people and read agreeable information, a behavior that leads to group polarization. Motivated by this scenario, we study how to take advantage of partial homophily to suggest agreeable content to users authored by people with opposite views on sensitive issues. We introduce a paradigm to present a data portrait of users, in which their characterizing topics are visualized and their corresponding tweets are displayed using an organic design. Among their tweets we inject recommended tweets from other people considering their views on sensitive issues in addition to topical relevance, indirectly motivating connections between dissimilar people. To evaluate our approach, we present a case study on Twitter about a sensitive topic in Chile, where we estimate user stances for regular people and find intermediary topics. We then evaluated our design in a user study. We found that recommending topically relevant content from authors with opposite views in a baseline interface had a negative emotional effect. We saw that our organic visualization design reverts that effect. We also observed significant individual differences linked to evaluation of recommendations. Our results suggest that organic visualization may revert the negative effects of providing potentially sensitive content.

cs.HC↗

arXiv2013

Ornitología Virtual: Caracterizando a #Chile en Twitter

Este artículo presenta un análisis de los tweets recolectados el 28 de Octubre de 2012, en el contexto de las elecciones municipales de 2012 en Chile. Dicho análisis se realiza mediante una metodología basada en literatura previa, en particular en técnicas de recuperación de la información y de análisis de espacios de información. Como resultado, se determinan: 1) características demográficas básicas de la población virtual chilena, incluyendo su distribución geográfica, 2) el contenido que caracteriza a cada región, y cómo fluye información entre regiones, y 3) el grado de representatividad de la población virtual participante en el evento con respecto a la población física. Se determina que la muestra obtenida es representativa de la población en términos de distribución geográfica, que el centralismo que afecta al país se ve reflejado en Twitter, y que, a pesar de los sesgos poblacionales, es posible identificar el contenido que caracteriza a cada región. Se finaliza con una discusión de las implicaciones y conclusiones prácticas de este trabajo, así como futuras aplicaciones.

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arXiv2013

Caracterizando la Web Chilena

This article presents a characterization of the web space from Chile in 2007. The characterization shows distributions of sites and domains, analysis of document content and server configuration. In addition, the network structure of the chilean Web is analyzed, determining components based on hyperlink structure at the document and site levels. Original Abstract: En este artículo se muestra una caracterización del espacio web de Chile para el año 2007. Se muestran distribuciones de sitios y dominios, caracterización del contenido en base a tipos de documento, asi como configuración de los servidores. Se estudia la estructura de la red creada mediante hipervínculos en los documentos y cómo las diferentes componentes de esta estructura varían cuando los hipervínculos son agregados a nivel de sitios.

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arXiv2013

Zahir: a Object-Oriented Framework for Computer Graphics

In this article we present Zahir, a framework for experimentation in Computer Graphics that provides a group of object-oriented base components that take care of common tasks in rendering techniques and algorithms, specially those of Non Photo-realistic Rendering (NPR). These components allow developers to implement rendering techniques and algorithms over static and animated meshes. Currently, Zahir is being used in a Master's Thesis and as support material in the undergraduate Computer Graphics course in University of Chile.

cs.GR↗

arXiv2013

Evolution of the Chilean Web: A Larger Study

In this paper we extend our previous and only study on the dynamics of the Chilean Web. This new study doubles the time period and to the best of our knowledge is the only study of its type known about any country in the Web. The new results corroborate the trends found before, in particular the exponential growth of the Web, and reinforce the conclusion that the Web is more chaotic than we would like. Hence, modeling most Web characteristics is not trivial.

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arXiv2013

#Santiago is not #Chile, or is it? A Model to Normalize Social Media Impact

Online social networks are known to be demographically biased. Currently there are questions about what degree of representativity of the physical population they have, and how population biases impact user-generated content. In this paper we focus on centralism, a problem affecting Chile. Assuming that local differences exist in a country, in terms of vocabulary, we built a methodology based on the vector space model to find distinctive content from different locations, and use it to create classifiers to predict whether the content of a micro-post is related to a particular location, having in mind a geographically diverse selection of micro-posts. We evaluate them in a case study where we analyze the virtual population of Chile that participated in the Twitter social network during an event of national relevance: the municipal (local governments) elections held in 2012. We observe that the participating virtual population is spatially representative of the physical population, implying that there is centralism in Twitter. Our classifiers out-perform a non geographically-diverse baseline at the regional level, and have the same accuracy at a provincial level. However, our approach makes assumptions that need to be tested in multi-thematic and more general datasets. We leave this for future work.

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