{"title":"Lp-norm spherical copulas","authors":"Carole Bernard , Alfred Müller , Marco Oesting","doi":"10.1016/j.jmva.2023.105262","DOIUrl":"10.1016/j.jmva.2023.105262","url":null,"abstract":"<div><p>In this paper we study <span><math><msub><mrow><mi>L</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span><span>-norm spherical copulas for arbitrary </span><span><math><mrow><mi>p</mi><mo>∈</mo><mrow><mo>[</mo><mn>1</mn><mo>,</mo><mi>∞</mi><mo>]</mo></mrow></mrow></math></span><span> and arbitrary dimensions<span>. The study is motivated by a conjecture that these distributions lead to a sharp bound for the value of a certain generalized mean difference. We fully characterize conditions for existence and uniqueness of </span></span><span><math><msub><mrow><mi>L</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span><span><span>-norm spherical copulas. Explicit formulas for their densities and correlation coefficients<span> are derived and the distribution of the radial part is determined. Moreover, </span></span>statistical inference and efficient simulation are considered.</span></p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105262"},"PeriodicalIF":1.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138503938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Copula modeling from Abe Sklar to the present day","authors":"Christian Genest , Ostap Okhrin , Taras Bodnar","doi":"10.1016/j.jmva.2023.105278","DOIUrl":"10.1016/j.jmva.2023.105278","url":null,"abstract":"<div><p>This paper provides a structured overview of the contents of the Special Issue of the <span><em>Journal of </em><em>Multivariate Analysis</em></span> on “Copula modeling from Abe Sklar to the present day,” along with a brief history of the development of the field.</p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105278"},"PeriodicalIF":1.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138503937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"fastMI: A fast and consistent copula-based nonparametric estimator of mutual information","authors":"Soumik Purkayastha , Peter X.-K. Song","doi":"10.1016/j.jmva.2023.105270","DOIUrl":"10.1016/j.jmva.2023.105270","url":null,"abstract":"<div><p><span>As a fundamental concept in information theory<span>, mutual information (</span></span><span><math><mrow><mi>M</mi><mi>I</mi></mrow></math></span>) has been commonly applied to quantify association between random vectors. Most existing nonparametric estimators of <span><math><mrow><mi>M</mi><mi>I</mi></mrow></math></span> have unstable statistical performance since they involve parameter tuning. We develop a consistent and powerful estimator, called <span>fastMI</span><span>, that does not incur any parameter tuning. Based on a copula formulation, </span><span>fastMI</span> estimates <span><math><mrow><mi>M</mi><mi>I</mi></mrow></math></span> by leveraging Fast Fourier transform-based estimation of the underlying density. Extensive simulation studies reveal that <span>fastMI</span> outperforms state-of-the-art estimators with improved estimation accuracy and reduced run time for large data sets. <span>fastMI</span> provides a powerful test for independence that exhibits satisfactory type I error control. Anticipating that it will be a powerful tool in estimating mutual information in a broad range of data, we develop an <span>R</span> package <span>fastMI</span> for broader dissemination.</p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105270"},"PeriodicalIF":1.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138516874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Penalized estimation of hierarchical Archimedean copula","authors":"Ostap Okhrin , Alexander Ristig","doi":"10.1016/j.jmva.2023.105274","DOIUrl":"10.1016/j.jmva.2023.105274","url":null,"abstract":"<div><p>This manuscript discusses a novel estimation approach for parametric hierarchical Archimedean copula. The parameters and structure of this copula are simultaneously estimated while imposing a non-concave penalty on differences between parameters which coincides with an implicit penalty on the copula’s structure. The asymptotic properties of the resulting penalized estimator are studied and small sample properties are illustrated using simulations.</p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105274"},"PeriodicalIF":1.6,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0047259X23001203/pdfft?md5=1aee43f0a4042437779957fee35e851c&pid=1-s2.0-S0047259X23001203-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138516881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A multivariate skew-normal-Tukey-h distribution","authors":"Sagnik Mondal, Marc G. Genton","doi":"10.1016/j.jmva.2023.105260","DOIUrl":"https://doi.org/10.1016/j.jmva.2023.105260","url":null,"abstract":"<div><p><span>We introduce a new family of multivariate distributions by taking the component-wise Tukey-</span><span><math><mi>h</mi></math></span> transformation of a random vector following a skew-normal distribution with an alternative parameterization. The proposed distribution is named the skew-normal-Tukey-<span><math><mi>h</mi></math></span> distribution and is an extension of the skew-normal distribution for handling heavy-tailed data. We compare this proposed distribution to the skew-<span><math><mi>t</mi></math></span><span><span> distribution, which is another extension of the skew-normal distribution for modeling tail-thickness, and demonstrate that when there are substantial differences in marginal kurtosis, the proposed distribution is more appropriate. Moreover, we derive many appealing </span>stochastic properties of the proposed distribution and provide a methodology for the estimation of the parameters that can be applied to large dimensions. Using simulations, as well as a wine and a wind speed data application, we illustrate how to draw inferences based on the multivariate skew-normal-Tukey-</span><span><math><mi>h</mi></math></span> distribution.</p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"200 ","pages":"Article 105260"},"PeriodicalIF":1.6,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138484142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Testing homogeneity in high dimensional data through random projections","authors":"Tao Qiu , Qintong Zhang , Yuanyuan Fang , Wangli Xu","doi":"10.1016/j.jmva.2023.105252","DOIUrl":"https://doi.org/10.1016/j.jmva.2023.105252","url":null,"abstract":"<div><p><span><span>Testing for homogeneity of two random vectors is a fundamental problem in statistics. In the past two decades, numerous efforts have been made to detect heterogeneity when the random vectors are multivariate or even high dimensional. Due to the “curse of dimensionality”, existing tests based on </span>Euclidean distance<span> may fail to capture the overall homogeneity in high-dimensional settings while can only capture the moment discrepancy. To address this issue, we propose a fully nonparametric test for homogeneity of two random vectors. Our method involves randomly selecting two subspaces consisting of components of the vectors, projecting the subspaces onto one-dimensional spaces, respectively, and constructing the test statistic using the Cramér–von Mises distance of the projections. To enhance the performance, we repeatedly implement this procedure to construct the final test statistic. Theoretically, if the replication time tends to infinity, we can avoid potential power loss caused by lousy directions. Owing to the </span></span><span><math><mi>U</mi></math></span><span>-statistic theory, the asymptotic null<span> distribution of our proposed test is standard normal, regardless of the parent distributions of the random samples and the relationship between data dimensions and sample sizes. As a result, no re-sampling procedure is needed to determine critical values. The empirical size and power of the proposed test are demonstrated through numerical simulations.</span></span></p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"200 ","pages":"Article 105252"},"PeriodicalIF":1.6,"publicationDate":"2023-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138453609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"High-dimensional factor copula models with estimation of latent variables","authors":"Xinyao Fan, Harry Joe","doi":"10.1016/j.jmva.2023.105263","DOIUrl":"10.1016/j.jmva.2023.105263","url":null,"abstract":"<div><p><span>Factor models are a parsimonious way to explain the dependence of variables using several latent variables. In Gaussian 1-factor and structural factor models (such as bi-factor and oblique factor) and their factor </span>copula<span><span> counterparts, factor scores or proxies are defined as conditional expectations of latent variables given the observed variables. With mild assumptions, the proxies are consistent for corresponding latent variables as the sample size and the number of observed variables linked to each latent variable go to infinity. When the </span>bivariate<span> copulas linking observed variables to latent variables are not assumed in advance, sequential procedures are used for latent variables estimation, copula family selection and parameter estimation. The use of proxy variables for factor copulas means that approximate log-likelihoods can be used to estimate copula parameters with less computational effort for numerical integration.</span></span></p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105263"},"PeriodicalIF":1.6,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138503936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A class of smooth, possibly data-adaptive nonparametric copula estimators containing the empirical beta copula","authors":"Ivan Kojadinovic , Bingqing Yi","doi":"10.1016/j.jmva.2023.105269","DOIUrl":"10.1016/j.jmva.2023.105269","url":null,"abstract":"<div><p>A broad class of smooth, possibly data-adaptive nonparametric copula<span> estimators that contains empirical Bernstein copulas introduced by Sancetta and Satchell (and thus the empirical beta copula proposed by Segers, Sibuya and Tsukahara) is studied. Within this class, a subclass of estimators that depend on a scalar parameter determining the amount of marginal smoothing and a functional parameter controlling the shape of the smoothing region is specifically considered. Empirical investigations of the influence of these parameters suggest to focus on two particular data-adaptive smooth copula estimators that were found to be uniformly better than the empirical beta copula in all of the considered Monte Carlo experiments. Finally, with future applications to change-point detection in mind, conditions under which related sequential empirical copula processes converge weakly are provided.</span></p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105269"},"PeriodicalIF":1.6,"publicationDate":"2023-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138503934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Comparison of correlation-based measures of concordance in terms of asymptotic variance","authors":"Takaaki Koike , Marius Hofert","doi":"10.1016/j.jmva.2023.105265","DOIUrl":"10.1016/j.jmva.2023.105265","url":null,"abstract":"<div><p><span><span><span>We compare measures of concordance that arise as Pearson’s linear correlation coefficient between two random variables transformed so that they follow the so-called concordance-inducing distributions. The class of such transformed </span>rank correlations includes Spearman’s rho, Blomqvist’s beta and van der Waerden’s coefficient. When only the </span>standard axioms<span> of measures of concordance are required, it is not always clear which transformed rank correlation is most suitable to use. To address this question, we compare measures of concordance in terms of their best and worst asymptotic variances of some canonical estimators over a certain set of </span></span>dependence structures. A simple criterion derived from this approach is that concordance-inducing distributions with smaller fourth moment are more preferable. In particular, we show that Blomqvist’s beta is the optimal transformed rank correlation in this sense, and Spearman’s rho outperforms van der Waerden’s coefficient. Moreover, we find that Kendall’s tau, although it is not a transformed rank correlation of that nature, shares a certain optimal structure with Blomqvist’s beta.</p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105265"},"PeriodicalIF":1.6,"publicationDate":"2023-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138503931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Multivariate tail dependence and local stochastic dominance","authors":"Karl Friedrich Siburg, Christopher Strothmann","doi":"10.1016/j.jmva.2023.105267","DOIUrl":"10.1016/j.jmva.2023.105267","url":null,"abstract":"<div><p><span>Given two multivariate copulas<span> with corresponding tail dependence functions, we investigate the relation between a natural tail dependence ordering and the order of local stochastic dominance. We show that, although the two orderings are not equivalent in general, they coincide for various important classes of copulas, among them all multivariate </span></span>Archimedean<span> and bivariate lower extreme value copulas. We illustrate the relevance of our results by an implication to risk management.</span></p></div>","PeriodicalId":16431,"journal":{"name":"Journal of Multivariate Analysis","volume":"201 ","pages":"Article 105267"},"PeriodicalIF":1.6,"publicationDate":"2023-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138516853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}