Estimation of a covariance matrix or its inverse plays a central role in many statistical methods. For these methods to work reliably, estimated matrices must not only be invertible but also well-conditioned. The current paper introduces a novel prior to ensure a well-conditioned maximum a posteriori (MAP) covariance estimate. The prior shrinks the sample covariance estimator towards a stable target and leads to a MAP estimator that is consistent and asymptotically efficient. Thus, the MAP estimator gracefully transitions towards the sample covariance matrix as the number of samples grows relative to the number of covariates. The utility of the MAP estimator is demonstrated in two standard applications - discriminant analysis and EM clustering - in this sampling regime.
Stable Estimation of a Covariance Matrix Guided by Nuclear Norm Penalties
Published 2013 in Computational Statistics & Data Analysis
ABSTRACT
PUBLICATION RECORD
- Publication year
2013
- Venue
Computational Statistics & Data Analysis
- Publication date
2013-05-14
- Fields of study
Mathematics, Computer Science, Medicine
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
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