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Publicações

Publicações por LIAAD

2019

Modelling Overdispersion with Integer-Valued Moving Average Processes

Autores
Silva, ME; Silva, I; Torres, C;

Publicação
Springer Proceedings in Mathematics and Statistics

Abstract
A new first-order integer-valued moving average, INMA(1), model based on the negative binomial thinning operation defined by Ristic et al. [21] is proposed and characterized. It is shown that this model has negative binomial (NB) marginal distribution when the innovations follow an NB distribution and therefore it can be used in situations where the data present overdispersion. Additionally, this model is extended to the bivariate context. The Generalized Method of Moments (GMM) is used to estimate the unknown parameters of the proposed models and the results of a simulation study that intends to investigate the performance of the method show that, in general, the estimates are consistent and symmetric. Finally, the proposed model is fitted to a real dataset and the quality of the adjustment is evaluated. © 2019, Springer Nature Switzerland AG.

2019

Bayesian Outlier Detection in Non-Gaussian Autoregressive Time Series

Autores
Silva, ME; Pereira, I; McCabe, B;

Publicação
JOURNAL OF TIME SERIES ANALYSIS

Abstract
This work investigates outlier detection and modelling in non-Gaussian autoregressive time series models with margins in the class of a convolution closed parametric family. This framework allows for a wide variety of models for count and positive data types. The article investigates additive outliers which do not enter the dynamics of the process but whose presence may adversely influence statistical inference based on the data. The Bayesian approach proposed here allows one to estimate, at each time point, the probability of an outlier occurrence and its corresponding size thus identifying the observations that require further investigation. The methodology is illustrated using simulated and observed data sets.

2019

Multiscale information storage of linear long-range correlated stochastic processes

Autores
Faes, L; Pereira, MA; Silva, ME; Pernice, R; Busacca, A; Javorka, M; Rocha, AP;

Publicação
PHYSICAL REVIEW E

Abstract
Information storage, reflecting the capability of a dynamical system to keep predictable information during its evolution over time, is a key element of intrinsic distributed computation, useful for the description of the dynamical complexity of several physical and biological processes. Here we introduce a parametric approach which allows one to compute information storage across multiple timescales in stochastic processes displaying both short-term dynamics and long-range correlations (LRC). Our analysis is performed in the popular framework of multiscale entropy, whereby a time series is first "coarse grained" at the chosen timescale through low-pass filtering and downsampling, and then its complexity is evaluated in terms of conditional entropy. Within this framework, our approach makes use of linear fractionally integrated autoregressive (ARFI) models to derive analytical expressions for the information storage computed at multiple timescales. Specifically, we exploit state space models to provide the representation of lowpass filtered and downsampled ARFI processes, from which information storage is computed at any given timescale relating the process variance to the prediction error variance. This enhances the practical usability of multiscale information storage, as it enables a computationally reliable quantification of a complexity measure which incorporates the effects of LRC together with that of short-term dynamics. The proposed measure is first assessed in simulated ARFI processes reproducing different types of autoregressive dynamics and different degrees of LRC, studying both the theoretical values and the finite sample performance. We find that LRC alter substantially the complexity of ARFI processes even at short timescales, and that reliable estimation of complexity can be achieved at longer timescales only when LRC are properly modeled. Then, we assess multiscale information storage in physiological time series measured in humans during resting state and postural stress, revealing unprecedented responses to stress of the complexity of heart period and systolic arterial pressure variability, which are related to the different role played by LRC in the two conditions.

2019

NStackSenti: Evaluation of a Multi-level Approach for Detecting the Sentiment of Users

Autores
Sohan, MF; Rahman, SSMM; Munna, MTA; Allayear, SM; Rahman, MH; Rahman, MM;

Publicação
Communications in Computer and Information Science - Next Generation Computing Technologies on Computational Intelligence

Abstract

2019

Prediction Model for Prevalence of Type-2 Diabetes Mellitus Complications Using Machine Learning Approach

Autores
Younus, M; Munna, MTA; Alam, MM; Allayear, SM; Ara, SJF;

Publicação
Studies in Big Data - Data Management and Analysis

Abstract

2019

Prediction model for prevalence of type-2 diabetes complications with ann approach combining with K-fold cross validation and K-means clustering

Autores
Munna M.T.A.; Alam M.M.; Allayear S.M.; Sarker K.; Ara S.J.F.;

Publicação
Advances in Intelligent Systems and Computing

Abstract
In today’s era, most of the people are suffering with chronic diseases because of their lifestyle, food habits and reduction in physical activities. Diabetes is one of the most common chronic diseases which has affected to the people of all ages. Diabetes complication arises in human body due to increase of blood glucose (sugar) level than the normal level. Type-2 diabetes is considered as one of the most prevalent endocrine disorders. In this circumstance, we have tried to apply Machine learning algorithm to create the statistical prediction based model that people having diabetes can be aware of their prevalence. The aim of this paper is to detect the prevalence of diabetes relevant complications among patients with Type-2 diabetes mellitus. The processing and statistical analysis we used are Scikit-Learn, and Pandas for Python. We also have used unsupervised Machine Learning approaches known as Artificial Neural Network (ANN) and K-means Clustering for developing classification system based prediction model to judge Type-2 diabetes mellitus chronic diseases.

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