## The Annals of Statistics

### Classification in general finite dimensional spaces with the k-nearest neighbor rule

#### Abstract

Given an $n$-sample of random vectors $(X_{i},Y_{i})_{1\leq i\leq n}$ whose joint law is unknown, the long-standing problem of supervised classification aims to optimally predict the label $Y$ of a given new observation $X$. In this context, the $k$-nearest neighbor rule is a popular flexible and intuitive method in non-parametric situations. Even if this algorithm is commonly used in the machine learning and statistics communities, less is known about its prediction ability in general finite dimensional spaces, especially when the support of the density of the observations is $\mathbb{R}^{d}$. This paper is devoted to the study of the statistical properties of the $k$-nearest neighbor rule in various situations. In particular, attention is paid to the marginal law of $X$, as well as the smoothness and margin properties of the regression function $\eta(X)=\mathbb{E}[Y|X]$. We identify two necessary and sufficient conditions to obtain uniform consistency rates of classification and derive sharp estimates in the case of the $k$-nearest neighbor rule. Some numerical experiments are proposed at the end of the paper to help illustrate the discussion.

#### Article information

Source
Ann. Statist., Volume 44, Number 3 (2016), 982-1009.

Dates
Received: November 2014
Revised: September 2015
First available in Project Euclid: 11 April 2016

Permanent link to this document
https://projecteuclid.org/euclid.aos/1460381684

Digital Object Identifier
doi:10.1214/15-AOS1395

Mathematical Reviews number (MathSciNet)
MR3485951

Zentralblatt MATH identifier
1338.62082

Subjects
Primary: 62G05: Estimation 62F15: Bayesian inference
Secondary: 62G20: Asymptotic properties

#### Citation

Gadat, Sébastien; Klein, Thierry; Marteau, Clément. Classification in general finite dimensional spaces with the k -nearest neighbor rule. Ann. Statist. 44 (2016), no. 3, 982--1009. doi:10.1214/15-AOS1395. https://projecteuclid.org/euclid.aos/1460381684

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#### Supplemental materials

• Supplement to “Classification in general finite dimensional spaces with the k-nearest neighbor rule”. Supplement contains some technical results and the proofs of Theorem 4.1, 4.2 and 4.5(i).