Abstract
Let y1, y2,..., yn∈ Rq be independent, identically distributed random vectors with nonsingular covariance matrix Σ, and let S = S(y1,..., yn) be an estimator for Σ. A quantity of particular interest is the condition number of Σ-1 S. If the yi are Gaussian and S is the sample covariance matrix, the condition number of Σ-1 S, i.e. the ratio of its extreme eigenvalues, equals 1 + Op((q/n)1/2) as q →∞ and q/n → 0. The present paper shows that the same result can be achieved with two estimators based on Tyler's (1987, Ann. Statist., 15, 234-251) M-functional of scatter, assuming only elliptical symmetry of ℒ(yi) or less. The main tool is a linear expansion for this M-functional which holds uniformly in the dimension q. As a by-product we obtain continuous Fréchet-differentiability with respect to weak convergence.
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References
Arcones, M. A. and Gine, E. (1993). Limit theorems for U-processes, Ann. Probab., 21, 1494–1542.
Bai, Z. D. and Wu, Y. (1994a). Limiting behavior of M-estimators of regression coefficients in high dimensional linear models. I. Scale-dependent case, J. Multivariate Anal., 51, 211–239.
Bai, Z. D. and Wu, Y. (1994b). Limiting behavior of M-estimators of regression coefficients in high dimensional linear models. II. Scale-invariant case, J. Multivariate Anal., 51, 240–251.
Bennett, G. (1962). Probability inequalities for the sum of independent random variables, J. Amer. Statist. Assoc., 57, 33–45.
Bickel, P. and Freedman, D. (1981). Some asymptotic theory for the bootstrap, Ann. Statist., 9, 1196–1217.
Clarke, B. R. (1983). Uniqueness and Fréchet differentiability of functional solutions to maximum likelihood type equations, Ann. Statist., 11, 1196–1205.
Dümbgen, L. (1997). The asymptotic behavior of Tyler's M-estimator of scatter in high dimension, Beitrag zur Statistik # 23, Heidelberg University.
Dümbgen, L. (1998). Perturbation inequalities and confidence sets for functions of a scatter matrix, J. Multivariate Anal., 65, 19–35.
Girko, V. L. (1995). Statistical Analysis of Observations of Increasing Dimension, Kluwer, Dordrecht.
Hoeffding, W. (1963). Probability inequalities for sums of bounded random variables, J. Amer. Statist. Assoc., 58, 13–30.
Huber, P. J. (1981). Robust Statistics, Wiley, New York.
Kent, J. T. and Tyler, D. E. (1988). Maximum likelihood estimation for the wrapped Cauchy distribution, Journal of Applied Statistics, 15, 247–254.
Kent, J. T. and Tyler, D. E. (1991). Redescending M-estimates of multivariate location and scatter, Ann. Statist., 19, 2102–2119.
Mammen, E. (1996). Empirical process of residuals for high-dimensional linear models, Ann. Statist., 24, 307–335.
Maronna, R. A. (1976). Robust M-estimators of multivariate location and scatter, Ann. Statist., 4, 51–67.
Nolan, D. and Pollard, D. (1987). U-processes: rates of convergence, Ann. Statist., 15, 780–799.
Pisier, G. (1983). Some applications of the metric entropy condition to harmonic analysis, Banach Spaces, Harmonic Analysis, and Probability Theory (eds. R. C. Blei and S. J. Sidney), Lecture Notes in Math., 995, 123–154, Springer, Berlin.
Pollard, D. (1990). Empirical Processes: Theory and Applications, NSF-CBMS Regionial Conference Series in Probability and Statistics, 2, IMS, Hayward, California.
Portnoy, S. (1984). Asymptotic behavior M-estimators of p regression parameters when p 2/n is large, I. Consistency, Ann. Statist., 12, 1298–1309.
Portnoy, S. (1985). Asymptotic behavior M-estimators of p regression parameters when p 2/n is large, II. Asymptotic normality, Ann. Statist., 13, 1403–1417.
Portnoy, S. (1988). Asymptotic behavior of likelihood methods for exponential families when the number of parameters tends to infinity, Ann. Statist., 16, 356–366.
Silverstein, J. W. (1985). The smallest eigenvalue of a large dimensional Wishart matrix, Ann. Probab., 13, 1364–1368.
Tyler, D. E. (1987). A distribution-free M-estimator of multivariate scatter, Ann. Statist., 15, 234–251.
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Dümbgen, L. On Tyler's M-Functional of Scatter in High Dimension. Annals of the Institute of Statistical Mathematics 50, 471–491 (1998). https://doi.org/10.1023/A:1003573311481
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DOI: https://doi.org/10.1023/A:1003573311481