robustbase: adjboxStats – R documentation

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adjboxStats

Statistics for Skewness-adjusted Boxplots

Description

Computes the “statistics” for producing boxplots adjusted for skewed distributions as proposed in Hubert and Vandervieren (2008), see adjbox.

Usage

adjboxStats(x, coef = 1.5, a = -4, b = 3, do.conf = TRUE, do.out = TRUE,
            ...)

Arguments

`x`	a numeric vector for which adjusted boxplot statistics are computed.
`coef`	number determining how far ‘whiskers’ extend out from the box, see `boxplot.stats`.
`a, b`	scaling factors multiplied by the medcouple `mc()` to determine outlyer boundaries; see the references.
`do.conf,do.out`	logicals; if `FALSE`, the `conf` or `out` component respectively will be empty in the result.
`...`	further optional arguments to be passed to `mc()`, such as `doReflect`.

Details

Given the quartiles Q1, Q3, the interquartile range IQR := Q3-Q1, and the medcouple M :=mc(x), c =coef, the “fence” is defined, for M ≥ 0 as

[Q1 - c*exp(a * M)*IQR, Q3 + c*exp(b * M)*IQR],

and for M < 0 as

[Q1 - c*exp(-b * M)*IQR, Q3 + c*exp(-a * M)*IQR],

and all observations x outside the fence, the “potential outliers”, are returned in out.

Note that a typo in robustbase version up to 0.7-8, for the (rare left-skewed) case where mc(x) < 0, lead to a “fence” not wide enough in the upper part, and hence less outliers there.

Value

A list with the components

`stats`	a vector of length 5, containing the extreme of the lower whisker, the lower hinge, the median, the upper hinge and the extreme of the upper whisker.
`n`	the number of observations
`conf`	the lower and upper extremes of the ‘notch’ (`if(do.conf)`). See `boxplot.stats`.
`fence`	length 2 vector of interval boundaries which define the non-outliers, and hence the whiskers of the plot.
`out`	the values of any data points which lie beyond the fence, and hence beyond the extremes of the whiskers.

Note

The code only slightly modifies the code of R's boxplot.stats.

Author(s)

R Core Development Team (boxplot.stats); adapted by Tobias Verbeke and Martin Maechler.

Examples

data(condroz)
adjboxStats(ccA <- condroz[,"Ca"])
adjboxStats(ccA, doReflect = TRUE)# small difference in fence

## Test reflection invariance [was not ok, up to and including robustbase_0.7-8]
a1 <- adjboxStats( ccA, doReflect = TRUE)
a2 <- adjboxStats(-ccA, doReflect = TRUE)

nm1 <- c("stats", "conf", "fence")
stopifnot(all.equal(       a1[nm1],
                    lapply(a2[nm1], function(u) rev(-u))),
          all.equal(a1[["out"]], -a2[["out"]]))

robustbase

Basic Robust Statistics

v0.93-7

GPL (>= 2)

Authors

Martin Maechler [aut, cre] (<https://orcid.org/0000-0002-8685-9910>), Peter Rousseeuw [ctb] (Qn and Sn), Christophe Croux [ctb] (Qn and Sn), Valentin Todorov [aut] (most robust Cov), Andreas Ruckstuhl [aut] (nlrob, anova, glmrob), Matias Salibian-Barrera [aut] (lmrob orig.), Tobias Verbeke [ctb, fnd] (mc, adjbox), Manuel Koller [aut] (mc, lmrob, psi-func.), Eduardo L. T. Conceicao [aut] (MM-, tau-, CM-, and MTL- nlrob), Maria Anna di Palma [ctb] (initial version of Comedian)

Initial release

2021-01-04