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Publications

Publications by João Gama

2013

On Predicting the Taxi-Passenger Demand: A Real-Time Approach

Authors
Moreira Matias, L; Gama, J; Ferreira, M; Mendes Moreira, J; Damas, L;

Publication
PROGRESS IN ARTIFICIAL INTELLIGENCE, EPIA 2013

Abstract
Informed driving is becoming a key feature to increase the sustainability of taxi companies. Some recent works are exploring the data broadcasted by each vehicle to provide live information for decision making. In this paper, we propose a method to employ a learning model based on historical GPS data in a real-time environment. Our goal is to predict the spatiotemporal distribution of the Taxi-Passenger demand in a short time horizon. We did so by using learning concepts originally proposed to a well-known online algorithm: the perceptron [1]. The results were promising: we accomplished a satisfactory performance to output the next prediction using a short amount of resources.

2017

Scalable Online Top-N Recommender Systems

Authors
Jorge, AM; Vinagre, J; Domingues, M; Gama, J; Soares, C; Matuszyk, P; Spiliopoulou, M;

Publication
E-COMMERCE AND WEB TECHNOLOGIES, EC-WEB 2016

Abstract
Given the large volumes and dynamics of data that recommender systems currently have to deal with, we look at online stream based approaches that are able to cope with high throughput observations. In this paper we describe work on incremental neighborhood based and incremental matrix factorization approaches for binary ratings, starting with a general introduction, looking at various approaches and describing existing enhancements. We refer to recent work on forgetting techniques and multidimensional recommendation. We will also focus on adequate procedures for the evaluation of online recommender algorithms.

2013

Special track on data streams

Authors
Rodrigues, PP; Bifet, A; Krishnaswamy, S; Gama, J;

Publication
Proceedings of the ACM Symposium on Applied Computing

Abstract

2013

Adaptive model rules from data streams

Authors
Almeida, E; Ferreira, C; Gama, J;

Publication
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract
Decision rules are one of the most expressive languages for machine learning. In this paper we present Adaptive Model Rules (AMRules), the first streaming rule learning algorithm for regression problems. In AMRules the antecedent of a rule is a conjunction of conditions on the attribute values, and the consequent is a linear combination of attribute values. Each rule uses a Page-Hinkley test to detect changes in the process generating data and react to changes by pruning the rule set. In the experimental section we report the results of AMRules on benchmark regression problems, and compare the performance of our system with other streaming regression algorithms. © 2013 Springer-Verlag.

2014

An eigenvector-based hotspot detection

Authors
T, HadiFanaee; Gama, Joao;

Publication
CoRR

Abstract

2014

An Incremental Probabilistic Model to Predict Bus Bunching in Real-Time

Authors
Moreira Matias, L; Gama, J; Mendes Moreira, J; de Sousa, JF;

Publication
ADVANCES IN INTELLIGENT DATA ANALYSIS XIII

Abstract
In this paper, we presented a probabilistic framework to predict Bus Bunching (BB) occurrences in real-time. It uses both historical and real-time data to approximate the headway distributions on the further stops of a given route by employing both offline and online supervised learning techniques. Such approximations are incrementally calculated by reusing the latest prediction residuals to update the further ones. These update rules extend the Perceptron's delta rule by assuming an adaptive beta value based on the current context. These distributions are then used to compute the likelihood of forming a bus platoon on a further stop - which may trigger an threshold-based BB alarm. This framework was evaluated using real-world data about the trips of 3 bus lines throughout an year running on the city of Porto, Portugal. The results are promising.

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