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Nonparametric estimators for the mean and the covariance functions of functional data are proposed. The setup covers a wide range of practical situations. The random trajectories are, not necessarily differentiable, have unknown regularity,…

Statistics Theory · Mathematics 2025-02-13 Steven Golovkine , Nicolas Klutchnikoff , Valentin Patilea

This article investigates nonparametric estimation of variance functions for functional data when the mean function is unknown. We obtain asymptotic results for the kernel estimator based on squared residuals. Similar to the finite…

Methodology · Statistics 2008-12-16 Heng Lian

Flexible estimation of the mean outcome under a treatment regimen (i.e., value function) is the key step toward personalized medicine. We define our target parameter as a conditional value function given a set of baseline covariates which…

Statistics Theory · Mathematics 2023-09-29 Ashkan Ertefaie , Luke Duttweiler , Brent A. Johnson , Mark J. van der Laan

In this paper we consider the problems of supervised classification and regression in the case where attributes and labels are functions: a data is represented by a set of functions, and the label is also a function. We focus on the use of…

Machine Learning · Computer Science 2016-11-03 Hachem Kadri , Emmanuel Duflos , Philippe Preux , Stéphane Canu , Alain Rakotomamonjy , Julien Audiffren

Situations of a functional predictor paired with a scalar response are increasingly encountered in data analysis. Predictors are often appropriately modeled as square integrable smooth random functions. Imposing minimal assumptions on the…

Statistics Theory · Mathematics 2009-09-08 Peter Hall , Hans-Georg Müller , Fang Yao

The main purpose is to estimate the regression function of a real random variable with functional explanatory variable by using a recursive nonparametric kernel approach. The mean square error and the almost sure convergence of a family of…

Statistics Theory · Mathematics 2013-08-07 Aboubacar Amiri , Christophe Crambes , Baba Thiam

In this work we are interested in the problems of supervised learning and variable selection when the input-output dependence is described by a nonlinear function depending on a few variables. Our goal is to consider a sparse nonparametric…

Machine Learning · Statistics 2012-08-14 Lorenzo Rosasco , Silvia Villa , Sofia Mosci , Matteo Santoro , Alessandro verri

In semivarying coefficient models for longitudinal/clustered data, usually of primary interest is usually the parametric component which involves unknown constant coefficients. First, we study semiparametric efficiency bound for estimation…

Methodology · Statistics 2015-09-15 Ming-Yen Cheng , Toshio Honda , Jialiang Li

We propose a novel nonparametric regression framework subject to the positive definiteness constraint. It offers a highly modular approach for estimating covariance functions of stationary processes. Our method can impose positive…

Methodology · Statistics 2023-04-27 Myeongjong Kang

Motivated by recent work involving the analysis of leveraging spatial correlations in sparsified mean estimation, we present a novel procedure for constructing covariance estimator. The proposed Random-knots (Random-knots-Spatial) and…

Methodology · Statistics 2025-11-25 Sijie Zheng , Fandong Meng , Jie Zhou

Linear discriminant analysis (LDA) is a widely used technique for data classification. The method offers adequate performance in many classification problems, but it becomes inefficient when the data covariance matrix is ill-conditioned.…

Machine Learning · Statistics 2024-02-08 Maaz Mahadi , Tarig Ballal , Muhammad Moinuddin , Tareq Y. Al-Naffouri , Ubaid M. Al-Saggaf

New estimators for the mean and the covariance function for partially observed functional data are proposed using a detour via the fundamental theorem of calculus. The new estimators allow for a consistent estimation of the mean and…

Methodology · Statistics 2018-08-01 Dominik Liebl , Stefan Rameseder

In this paper we present a nonparametric method for extending functional regression methodology to the situation where more than one functional covariate is used to predict a functional response. Borrowing the idea from Kadri et al.…

Machine Learning · Statistics 2013-01-16 Hachem Kadri , Philippe Preux , Emmanuel Duflos , Stéphane Canu

In nonparametric regression analysis, errors are possibly correlated in practice, and neglecting error correlation can undermine most bandwidth selection methods. When no prior knowledge or parametric form of the correlation structure is…

Methodology · Statistics 2025-04-29 Sisheng Liu , Xiaoli Kong

We present a functional data analysis (FDA) framework based on explicit orthonormal basis expansion for modeling and denoising complex biomedical signals. Observed functional data are represented as smooth functions in a Hilbert space, and…

Computation · Statistics 2026-02-16 Moo K. Chung

We analyze the problem of regression when both input covariates and output responses are functions from a nonparametric function class. Function to function regression (FFR) covers a large range of interesting applications including…

Machine Learning · Statistics 2014-10-29 Junier Oliva , Willie Neiswanger , Barnabas Poczos , Eric Xing , Jeff Schneider

We consider the problem of estimating the slope parameter in functional linear regression, where scalar responses Y1,...,Yn are modeled in dependence of second order stationary random functions X1,...,Xn. An orthogonal series estimator of…

Statistics Theory · Mathematics 2009-01-28 Jan Johannes

Dimension reduction is crucial in functional data analysis (FDA). The key tool to reduce the dimension of the data is functional principal component analysis. Existing approaches for functional principal component analysis usually involve…

Methodology · Statistics 2024-06-21 Steven Golovkine , Edward Gunning , Andrew J. Simpkin , Norma Bargary

This paper considers nonparametric identification and estimation of the regression function when a covariate is mismeasured. The measurement error need not be classical. Employing the small measurement error approximation, we establish…

Econometrics · Economics 2024-03-19 Kirill S. Evdokimov , Andrei Zeleneev

This paper studies sparse covariance operator estimation for nonstationary processes with sharply varying marginal variance and small correlation lengthscale. We introduce a covariance operator estimator that adaptively thresholds the…

Statistics Theory · Mathematics 2025-06-23 Omar Al-Ghattas , Daniel Sanz-Alonso