Separation-based parameterization strategies for estimation of restricted covariance matrices in multivariate model systems

IF 2.8 3区 经济学 Q1 ECONOMICS Journal of Choice Modelling Pub Date : 2023-06-01 DOI:10.1016/j.jocm.2023.100411
Shobhit Saxena , Chandra R. Bhat , Abdul Rawoof Pinjari
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引用次数: 1

Abstract

Many multivariate model systems involve the estimation of a covariance matrix that must be positive-definite. A common strategy to ensure positive definiteness of the covariance matrix is through the use of a Cholesky parameterization of the covariance matrix. However, several model systems require imposing restrictions on the elements of the covariance elements. For instance, modelling systems may require fixing some (or all) of the diagonal elements in the covariance matrix to unity due to identification considerations. However, imposing such restrictions using the traditional Cholesky decomposition approach is not feasible and requires the additional parameterization of the Cholesky elements.

In this paper, we explore a separation-based strategy with spherical parameterization of the Cholesky matrix to impose restrictions on the covariance matrix. Importantly, using this separation-based parameterization strategy, we also explore the possibility of restricting some covariance (or correlation) terms to zero. The effectiveness of the proposed strategy is assessed through extensive simulation experiments. The results from the simulation experiments highlight better performance of the separation-based strategy in terms of recovery of model parameters – particularly those in the covariance matrix, than the traditional Cholesky parameterization approach. Finally, the proposed strategy is implemented in a joint multivariate binary probit ordered probit model system to analyze the usage (and the extent of use) of non-private modes of transportation in Bengaluru, India. In doing so, the proposed strategy is implemented to restrict several correlations to zero, thus avoiding the estimation of a profligate correlation matrix and substantially easing the estimation process.

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基于分离的多变量模型系统中受限协方差矩阵估计的参数化策略
许多多变量模型系统涉及协方差矩阵的估计,该协方差矩阵必须是正定的。确保协方差矩阵的正定性的常用策略是通过使用协方差矩阵的Cholesky参数化。然而,一些模型系统需要对协方差元素的元素施加限制。例如,由于识别考虑,建模系统可能需要将协方差矩阵中的一些(或全部)对角元素固定为1。然而,使用传统的Cholesky分解方法施加这样的限制是不可行的,并且需要对Cholesky元素进行额外的参数化。在本文中,我们探索了一种基于分离的策略,该策略具有Cholesky矩阵的球面参数化,以对协方差矩阵施加限制。重要的是,使用这种基于分离的参数化策略,我们还探索了将某些协方差(或相关性)项限制为零的可能性。通过大量的仿真实验对所提出的策略的有效性进行了评估。模拟实验的结果突出表明,与传统的Cholesky参数化方法相比,基于分离的策略在恢复模型参数(尤其是协方差矩阵中的参数)方面具有更好的性能。最后,在一个联合的多元二元probit有序probit模型系统中实现了所提出的策略,以分析印度班加罗尔非私人交通方式的使用情况(以及使用程度)。在这样做的过程中,所提出的策略被实现为将几个相关性限制为零,从而避免了对挥霍的相关性矩阵的估计,并大大简化了估计过程。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
4.10
自引率
12.50%
发文量
31
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