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- research-articleSeptember 2024
Shrinkage for extreme partial least-squares
AbstractThis work focuses on dimension-reduction techniques for modelling conditional extreme values. Specifically, we investigate the idea that extreme values of a response variable can be explained by nonlinear functions derived from linear projections ...
- rapid-communicationJuly 2024
Bootstraps regularize singular correlation matrices
Journal of Computational and Applied Mathematics (JCAM), Volume 449, Issue Chttps://doi.org/10.1016/j.cam.2024.115958AbstractI show analytically that the average of k bootstrapped correlation matrices rapidly becomes positive-definite as k increases, which provides a simple approach to regularize singular Pearson correlation matrices. If n is the order of the matrix ...
- research-articleNovember 2023
Bayesian analysis of longitudinal data via empirical likelihood
Computational Statistics & Data Analysis (CSDA), Volume 187, Issue Chttps://doi.org/10.1016/j.csda.2023.107785AbstractLongitudinal data consists of repeated observations that are typically correlated, which makes the likelihood-based inference challenging. This limits the use of Bayesian methods for longitudinal data in many general situations. To ...
- research-articleJune 2023
Multi-step estimators and shrinkage effect in time series models
Computational Statistics (CSTAT), Volume 39, Issue 3Pages 1203–1239https://doi.org/10.1007/s00180-023-01377-xAbstractMany modern statistical models are used for both insight and prediction when applied to data. When models are used for prediction one should optimise parameters through a prediction error loss function. Estimation methods based on multiple steps ...
- research-articleMay 2023
An image-based meso-scale model for the hygro-mechanical time-dependent analysis of concrete
Computational Mechanics (SPCM), Volume 72, Issue 6Pages 1191–1214https://doi.org/10.1007/s00466-023-02344-5AbstractA new computational framework is developed in this paper for investigating the time-dependent behaviour of concrete including creep, shrinkage and cracking. The developed model aims to explain certain aspects of the time-dependent cracking and ...
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- research-articleMarch 2023
Predictive stability criteria for penalty selection in linear models
Computational Statistics (CSTAT), Volume 39, Issue 3Pages 1241–1280https://doi.org/10.1007/s00180-023-01342-8AbstractChoosing a shrinkage method can be done by selecting a penalty from a list of pre-specified penalties or by constructing a penalty based on the data. If a list of penalties for a class of linear models is given, we introduce a predictive stability ...
- research-articleMarch 2023
A sparse Bayesian hierarchical vector autoregressive model for microbial dynamics in a wastewater treatment plant
- Naomi E. Hannaford,
- Sarah E. Heaps,
- Tom M.W. Nye,
- Thomas P. Curtis,
- Ben Allen,
- Andrew Golightly,
- Darren J. Wilkinson
Computational Statistics & Data Analysis (CSDA), Volume 179, Issue Chttps://doi.org/10.1016/j.csda.2022.107659AbstractProper function of a wastewater treatment plant (WWTP) relies on maintaining a delicate balance between a multitude of competing microorganisms. Gaining a detailed understanding of the complex network of interactions therein is essential to ...
Highlights- Vector autoregressive models can detect interactions in microbial communities.
- Regularised horseshoe performs well as a prior for a sparse autoregressive matrix.
- Including environmental factors improves inference of microbial ...
- research-articleNovember 2022
Adaptive step-length selection in gradient boosting for Gaussian location and scale models
Computational Statistics (CSTAT), Volume 37, Issue 5Pages 2295–2332https://doi.org/10.1007/s00180-022-01199-3AbstractTuning of model-based boosting algorithms relies mainly on the number of iterations, while the step-length is fixed at a predefined value. For complex models with several predictors such as Generalized additive models for location, scale and shape ...
- ArticleOctober 2022
Kernel Relative-prototype Spectral Filtering for Few-Shot Learning
AbstractFew-shot learning performs classification tasks and regression tasks on scarce samples. As one of the most representative few-shot learning models, Prototypical Network represents each class as sample average, or a prototype, and measures the ...
- research-articleMay 2022
Smoothly adaptively centered ridge estimator
Journal of Multivariate Analysis (JMUL), Volume 189, Issue Chttps://doi.org/10.1016/j.jmva.2021.104882AbstractWith a focus on linear models with smooth functional covariates, we propose a penalization framework (SACR) based on the nonzero centered ridge, where the center of the penalty is adaptively reweighted, starting from the ordinary ridge ...
- research-articleMarch 2021
Usage of the GO estimator in high dimensional linear models
Computational Statistics (CSTAT), Volume 36, Issue 1Pages 217–239https://doi.org/10.1007/s00180-020-01001-2AbstractThis paper discusses simultaneous parameter estimation and variable selection and presents a new penalized regression method. The method is based on the idea that the coefficient estimates are shrunken towards a predetermined coefficient vector ...
- research-articleSeptember 2020
Modelling rankings in R: the PlackettLuce package
Computational Statistics (CSTAT), Volume 35, Issue 3Pages 1027–1057https://doi.org/10.1007/s00180-020-00959-3AbstractThis paper presents the R package PlackettLuce, which implements a generalization of the Plackett–Luce model for rankings data. The generalization accommodates both ties (of arbitrary order) and partial rankings (complete rankings of subsets of ...
- research-articleJanuary 2020
Multivariate estimation of Poisson parameters
Journal of Multivariate Analysis (JMUL), Volume 175, Issue Chttps://doi.org/10.1016/j.jmva.2019.104545AbstractThis paper is devoted to the multivariate estimation of a vector of Poisson means. A novel loss function that penalises bad estimates of each of the parameters and also the sum (or equivalently the mean) of the parameters is ...
- research-articleNovember 2019
Bounded depth circuits with weighted symmetric gates: Satisfiability, lower bounds and compression
Journal of Computer and System Sciences (JCSS), Volume 105, Issue CPages 87–103https://doi.org/10.1016/j.jcss.2019.04.004AbstractA Boolean function f : { 0 , 1 } n → { 0 , 1 } is weighted symmetric if there exist a function g : Z → { 0 , 1 } and integers w 0 , w 1 , … , w n such that f ( x 1 , … , x n ) = g ( w 0 + ∑ i = 1 n w i x i ) holds. In this paper, we ...
- research-articleNovember 2019
Weighted covariance matrix estimation
Computational Statistics & Data Analysis (CSDA), Volume 139, Issue CPages 82–98https://doi.org/10.1016/j.csda.2019.04.017AbstractThe paper proposes a cross-validated linear shrinkage estimation for population covariance matrices. Moreover we also propose a novel weighted estimator based on the thresholding and shrinkage methods for high dimensional datasets. It ...
- ArticleSeptember 2019
Bayesian Generalized Horseshoe Estimation of Generalized Linear Models
Machine Learning and Knowledge Discovery in DatabasesPages 598–613https://doi.org/10.1007/978-3-030-46147-8_36AbstractBayesian global-local shrinkage estimation with the generalized horseshoe prior represents the state-of-the-art for Gaussian regression models. The extension to non-Gaussian data, such as binary or Student-t regression, is usually done by ...
- research-articleSeptember 2019
Prediction and calibration for multiple correlated variables
Journal of Multivariate Analysis (JMUL), Volume 173, Issue CPages 313–327https://doi.org/10.1016/j.jmva.2019.03.001AbstractThe standard approach for prediction of multiple correlated outcome measures overpredicts the unknown observation in the linear model setup if associated covariate measures follow a certain distribution. It is desired to have a ...
- research-articleMay 2019
Microwave power adjusting during potato slice drying process using machine vision
Computers and Electronics in Agriculture (COEA), Volume 160, Issue CPages 40–50https://doi.org/10.1016/j.compag.2019.03.013Highlights- Developing an image processing algorithm for segmenting and separating the center potato slice from other slices.
In this study, machine vision was used for measuring area shrinkage of potato slices during thin layer drying process and then an artificial neural network (ANN) and linear models were investigated to predict moisture content (MC) of ...
- research-articleApril 2019
Pseudorandomness from Shrinkage
Journal of the ACM (JACM), Volume 66, Issue 2Article No.: 11, Pages 1–16https://doi.org/10.1145/3230630One powerful theme in complexity theory and pseudorandomness in the past few decades has been the use of lower bounds to give pseudorandom generators (PRGs). However, the general results using this hardness vs. randomness paradigm suffer from a ...
- articleJanuary 2019
A Variable Step-Size Shrinkage Set-Membership Affine Projection Algorithm for Noisy Input
Circuits, Systems, and Signal Processing (CSSP), Volume 38, Issue 1Pages 455–469https://doi.org/10.1007/s00034-018-0851-3To solve the conflicting requirement of fast convergence and low steady-state misalignment, a variable step-size shrinkage set-membership affine projection algorithm is proposed, which is efficient for the correlated input signal and noisy input ...