shorth: A location estimator based on the shorth

In Bioconductor/genefilter: genefilter: methods for filtering genes from high-throughput experiments

A location estimator based on the shorth

Description

A location estimator based on the shorth

Usage

shorth(x, na.rm=FALSE, tie.action="mean", tie.limit=0.05)

Arguments

x	Numeric
na.rm	Logical. If TRUE, then non-finite (according to is.finite) values in x are ignored. Otherwise, presence of non-finite or NA values will lead to an error message.
tie.action	Character scalar. See details.
tie.limit	Numeric scalar. See details.

Details

The shorth is the shortest interval that covers half of the values in x. This function calculates the mean of the x values that lie in the shorth. This was proposed by Andrews (1972) as a robust estimator of location.

Ties: if there are multiple shortest intervals, the action specified in ties.action is applied. Allowed values are mean (the default), max and min. For mean, the average value is considered; however, an error is generated if the start indices of the different shortest intervals differ by more than the fraction tie.limit of length(x). For min and max, the left-most or right-most, respectively, of the multiple shortest intervals is considered.

Rate of convergence: as an estimator of location of a unimodal distribution, under regularity conditions, the quantity computed here has an asymptotic rate of only n^{-1/3} and a complicated limiting distribution.

See half.range.mode for an iterative version that refines the estimate iteratively and has a builtin bootstrapping option.

Value

The mean of the x values that lie in the shorth.

Author(s)

Wolfgang Huber http://www.ebi.ac.uk/huber, Ligia Pedroso Bras

References

• G Sawitzki, “The Shorth Plot.” Available at http://lshorth.r-forge.r-project.org/TheShorthPlot.pdf

• DF Andrews, “Robust Estimates of Location.” Princeton University Press (1972).

• R Grueble, “The Length of the Shorth.” Annals of Statistics 16, 2:619-628 (1988).

• DR Bickel and R Fruehwirth, “On a fast, robust estimator of the mode: Comparisons to other robust estimators with applications.” Computational Statistics & Data Analysis 50, 3500-3530 (2006).

See Also

half.range.mode

Examples

 
  x = c(rnorm(500), runif(500) * 10)
  methods = c("mean", "median", "shorth", "half.range.mode")
  ests = sapply(methods, function(m) get(m)(x))

  if(interactive()) {
    colors = 1:4
    hist(x, 40, col="orange")
    abline(v=ests, col=colors, lwd=3, lty=1:2)
    legend(5, 100, names(ests), col=colors, lwd=3, lty=1:2) 
  }

Bioconductor/genefilter documentation built on Nov. 2, 2024, 7:24 a.m.