car: symbox – R documentation

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symbox

Boxplots for transformations to symmetry

Description

symbox first transforms x to each of a series of selected powers, with each transformation standardized to mean 0 and standard deviation 1. The results are then displayed side-by-side in boxplots, permiting a visual assessment of which power makes the distribution reasonably symmetric.

Usage

symbox(x, ...)
## S3 method for class 'formula'
symbox(formula, data=NULL, subset, na.action=NULL, ylab,  ...)
## Default S3 method:
symbox(x, powers = c(-1, -0.5, 0, 0.5, 1), start, 
	trans=bcPower, xlab="Powers", ylab, ...)

Arguments

`x`	a numeric vector.
`formula`	a one-sided formula specifying a single numeric variable.
`data, subset, na.action`	as for statistical modeling functions (see, e.g., `lm`).
`xlab, ylab`	axis labels; if `ylab` is missing, a label will be supplied.
`powers`	a vector of selected powers to which `x` is to be raised. For meaningful comparison of powers, `1` should be included in the vector of powers.
`start`	a constant to be added to `x`. If `start` is missing and `trans` is `bcPower` (the default) or `bcnPower`, then a start will be automatically generated if there are zero or negative values in `x`, and a warning will be printed; the auto-generated `start` is the absolute value of the minimum `x` plus 1 percent of the range of `x`.
`trans`	a transformation function whose first argument is a numeric vector and whose second argument is a transformation parameter, given by the `powers` argument; the default is `bcPower`, and another possibility is `yjPower`. `bcnPower` may also be used, in which case the `gamma` parameter is set to the value of `start`.
`...`	arguments to be passed down.

Value

as returned by boxplot.

Author(s)

Gregor Gorjanc, John Fox jfox@mcmaster.ca.

References

Fox, J. and Weisberg, S. (2019) An R Companion to Applied Regression, Third Edition. Sage.

Examples

symbox(~ income, data=Prestige)

car

Companion to Applied Regression

v3.0-10

GPL (>= 2)

Authors

John Fox [aut, cre], Sanford Weisberg [aut], Brad Price [aut], Daniel Adler [ctb], Douglas Bates [ctb], Gabriel Baud-Bovy [ctb], Ben Bolker [ctb], Steve Ellison [ctb], David Firth [ctb], Michael Friendly [ctb], Gregor Gorjanc [ctb], Spencer Graves [ctb], Richard Heiberger [ctb], Pavel Krivitsky [ctb], Rafael Laboissiere [ctb], Martin Maechler [ctb], Georges Monette [ctb], Duncan Murdoch [ctb], Henric Nilsson [ctb], Derek Ogle [ctb], Brian Ripley [ctb], William Venables [ctb], Steve Walker [ctb], David Winsemius [ctb], Achim Zeileis [ctb], R-Core [ctb]

Initial release

2020-09-23