# boxcox {MASS}

### Description

Computes and optionally plots profile log-likelihoods for the parameter of the Box-Cox power transformation.

### Usage

boxcox(object, ...) ## S3 method for class 'default': boxcox((object, lambda = seq(-2, 2, 1/10), plotit = TRUE, interp, eps = 1/50, xlab = expression(lambda), ylab = "log-Likelihood", ...)) ## S3 method for class 'formula': boxcox((object, lambda = seq(-2, 2, 1/10), plotit = TRUE, interp, eps = 1/50, xlab = expression(lambda), ylab = "log-Likelihood", ...)) ## S3 method for class 'lm': boxcox((object, lambda = seq(-2, 2, 1/10), plotit = TRUE, interp, eps = 1/50, xlab = expression(lambda), ylab = "log-Likelihood", ...))

### Arguments

- object
- a formula or fitted model object. Currently only
`lm`

and`aov`

objects are handled. - lambda
- vector of values of
`lambda`

-- default (-2, 2) in steps of 0.1. - plotit
- logical which controls whether the result should be plotted.
- interp
- logical which controls whether spline interpolation is used. Default to
`TRUE`

if plotting with`lambda`

of length less than 100. - eps
- Tolerance for
`lambda = 0`

; defaults to 0.02. - xlab
- defaults to
`"lambda"`

. - ylab
- defaults to
`"log-Likelihood"`

. - ...
- additional parameters to be used in the model fitting.

### Values

A list of the `lambda`

vector and the computed profile log-likelihood vector, invisibly if the result is plotted.

### Side Effects

If `plotit = TRUE`

plots log-likelihood *vs* `lambda`

and indicates a 95% confidence interval about the maximum observed value of `lambda`

. If `interp = TRUE`

, spline interpolation is used to give a smoother plot.

### References

Box, G. E. P. and Cox, D. R. (1964) An analysis of transformations (with discussion). *Journal of the Royal Statistical Society B*, **26**, 211--252. Venables, W. N. and Ripley, B. D. (2002) *Modern Applied Statistics with S.* Fourth edition. Springer.

### Examples

Documentation reproduced from package MASS, version 7.3-45. License: GPL-2 | GPL-3