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.

References

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

See Also

boxplot, boxcox, box.cox

Examples

data(Prestige)
symbox(Prestige$income)

[Package car version 1.0-17 Index]