`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.

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

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.

as returned by `boxplot`

.

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

# NOT RUN { symbox(~ income, data=Prestige) # }