dplR (version 1.2.4)

tbrm: Calculates Tukey's Biweight Robust Mean

Description

This calculates a robust average that is unaffected by outliers.

Usage

tbrm(x, C = 9)

Arguments

x

a numeric vector

C

a constant. C is preassigned a value of 9 according to the Cook reference below but other values are possible.

Value

• A numeric mean.

Details

This is a one step computation that follows the Affy whitepaper below see page 22. This function is called by chron to calculate a robust mean. C determines the point at which outliers are given a weight of 0 and therefore do not contribute to the calculation of the mean. C=9 sets values roughly +/-6 standard deviations to 0. C=6 is also used in tree-ring chronology development. Cook and Kairiukstis (1990) have further details.

References

Statistical Algorithms Description Document, 2002, Affymetrix. p22. Cook, E. R. and Kairiukstis, L.A. (1990) Methods of Dendrochronology: Applications in the Environmental Sciences. Springer. ISBN-13: 978-0792305866. Mosteller, F. and Tukey, J. W. (1977) Data Analysis and Regression: a second course in statistics. Addison-Wesley. ISBN-13: 978-0201048544.

See Also

chron

Examples

tbrm(rnorm(100))

  # Compare
  data(co021)
  co021.rwi <- detrend(co021,method = "Spline")
  crn1 <- apply(co021.rwi,1,tbrm)
  crn2 <- chron(co021.rwi)
  cor(crn1,crn2[,1])