symbox {car}R Documentation

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, powers=c(-1, -.5, 0, .5, 1), start=0)

Arguments

x a numeric vector.
powers a vector of selected powers to which x is to be raised. A power of 0 is taken to mean $log(x)$. Negative powers are taken to mean $-x^p$, to preserve the order of the data. For meaningful comparison of powers, 1 should be included in the vector of powers.
start a constant to be added to x; after adding the start, all data values must be positive.

Value

as returned by boxplot.

Author(s)

Gregor Gorjanc, John Fox jfox@mcmaster.ca

References

Friendly, M. (2005) SAS System for Statistical Graphics, 2nd Edition. SAS Institute (In preparation).

See Also

boxplot, boxcox, box.cox

Examples

symbox(Prestige$income)

[Package car version 1.1-0 Index]