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Publicações

Publicações por Paula Brito

2015

Modeling Interval Time Series with Space-Time Processes

Autores
Teles, P; Brito, P;

Publicação
COMMUNICATIONS IN STATISTICS-THEORY AND METHODS

Abstract
We consider interval-valued time series, that is, series resulting from collecting real intervals as an ordered sequence through time. Since the lower and upper bounds of the observed intervals at each time point are in fact values of the same variable, they are naturally related. We propose modeling interval time series with space-time autoregressive models and, based on the process appropriate for the interval bounds, we derive the model for the intervals' center and radius. A simulation study and an application with data of daily wind speed at different meteorological stations in Ireland illustrate that the proposed approach is appropriate and useful.

2017

Off the beaten track: A new linear model for interval data

Autores
Dias, S; Brito, P;

Publicação
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
We propose a new linear regression model for interval-valued variables. The model uses quantile functions to represent the intervals, thereby considering the distributions within them. In this paper we study the special case where the Uniform distribution is assumed in each observed interval, and we analyze the extension to the Symmetric Triangular distribution. The parameters of the model are obtained solving a constrained quadratic optimization problem that uses the Mallows distance between quantile functions. As in the classical case, a goodness-of-fit measure is deduced. Two applications on up-to-date fields are presented: one predicting duration of unemployment and the other allowing forecasting burned area by forest fires.

2015

Linear Regression Model with Histogram-Valued Variables

Autores
Dias, S; Brito, P;

Publicação
STATISTICAL ANALYSIS AND DATA MINING

Abstract
Histogram-valued variables are a particular kind of variables studied in Symbolic Data Analysis where to each entity under analysis corresponds a distribution that may be represented by a histogram or by a quantile function. Linear regression models for this type of data are necessarily more complex than a simple generalization of the classical model: the parameters cannot be negative; still the linear relation between the variables must be allowed to be either direct or inverse. In this work, we propose a new linear regression model for histogram-valued variables that solves this problem, named Distribution and Symmetric Distribution Regression Model. To determine the parameters of this model, it is necessary to solve a quadratic optimization problem, subject to non-negativity constraints on the unknowns; the error measure between the predicted and observed distributions uses the Mallows distance. As in classical analysis, the model is associated with a goodness-of-fit measure whose values range between 0 and 1. Using the proposed model, applications with real and simulated data are presented.

2015

Symbolic Data Analysis and Visualization: Special Issue in honor of Monique Noirhomme-Fraiture

Autores
Venturini, G; Brito, P;

Publicação
Symbolic Data Analysis and Visualization

Abstract

2017

Exploratory data analysis for interval compositional data

Autores
Hron, K; Brito, P; Filzmoser, P;

Publicação
ADVANCES IN DATA ANALYSIS AND CLASSIFICATION

Abstract
Compositional data are considered as data where relative contributions of parts on a whole, conveyed by (log-)ratios between them, are essential for the analysis. In Symbolic Data Analysis (SDA), we are in the framework of interval data when elements are characterized by variables whose values are intervals on representing inherent variability. In this paper, we address the special problem of the analysis of interval compositions, i.e., when the interval data are obtained by the aggregation of compositions. It is assumed that the interval information is represented by the respective midpoints and ranges, and both sources of information are considered as compositions. In this context, we introduce the representation of interval data as three-way data. In the framework of the log-ratio approach from compositional data analysis, it is outlined how interval compositions can be treated in an exploratory context. The goal of the analysis is to represent the compositions by coordinates which are interpretable in terms of the original compositional parts. This is achieved by summarizing all relative information (logratios) about each part into one coordinate from the coordinate system. Based on an example from the European Union Statistics on Income and Living Conditions (EU-SILC), several possibilities for an exploratory data analysis approach for interval compositions are outlined and investigated.

2015

Editorial for Special Issue on Symbolic Data Analysis

Autores
Brito, P; Noirhomme Fraiture, M; Arroyo, J;

Publicação
ADVANCES IN DATA ANALYSIS AND CLASSIFICATION

Abstract

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