robCov: Robust covariance matrix estimation

Description Usage Arguments Details Value Author(s) References Examples

View source: R/robCov.R View source: R/I_robCov.R

Description

Obtains a robust estimate of the covariance matrix of a sample of multivariate data, using Campbell's (1980) method as described on p231-235 of Krzanowski (1988).

Usage

1
  robCov(sY, alpha = 2, beta = 1.25)

Arguments

sY

A matrix, where each column is a replicate observation on a multivariate r.v.

alpha

tuning parameter, see details.

beta

tuning parameter, see details.

Details

Campbell (1980) suggests an estimator of the covariance matrix which downweights observations at more than some Mahalanobis distance d.0 from the mean. d.0 is sqrt(nrow(sY))+alpha/sqrt(2). Weights are one for observations with Mahalanobis distance, d, less than d.0. Otherwise weights are d.0*exp(-.5*(d-d.0)^2/beta)/d. The defaults are as recommended by Campbell. This routine also uses pre-conditioning to ensure good scaling and stable numerical calculations.

Value

A list where:

Author(s)

Simon N. Wood, maintained by Matteo Fasiolo <matteo.fasiolo@gmail.com>.

References

Krzanowski, W.J. (1988) Principles of Multivariate Analysis. Oxford. Campbell, N.A. (1980) Robust procedures in multivariate analysis I: robust covariance estimation. JRSSC 29, 231-237.

Examples

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p <- 5;n <- 100
Y <- matrix(runif(p*n),p,n)
robCov(Y)

synlik documentation built on May 29, 2017, 12:16 p.m.

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