# symbox

From car v2.0-20
by John Fox

##### Boxplots for transformations to symmetry

`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.

- Keywords
- hplot

##### Usage

```
symbox(x, ...)
## S3 method for class 'formula':
symbox(formula, data=NULL, subset, na.action=NULL, ylab, ...)
## S3 method for class 'default':
symbox(x, powers = c(-1, -0.5, 0, 0.5, 1), start=0,
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`

. - 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 - ...
- arguments to be passed down.

##### Value

- as returned by
`boxplot`

.

##### References

Fox, J. and Weisberg, S. (2011)
*An R Companion to Applied Regression*, Second Edition. Sage.

##### See Also

##### Examples

`symbox(~ income, data=Prestige)`

*Documentation reproduced from package car, version 2.0-20, License: GPL (>= 2)*

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