boxTidwell: Box-Tidwell Transformations

In car: Companion to Applied Regression

Box-Tidwell Transformations

Description

Computes the Box-Tidwell power transformations of the predictors in a linear model.

Usage

boxTidwell(y, ...)

## S3 method for class 'formula'
boxTidwell(formula, other.x=NULL, data=NULL, subset, 
  na.action=getOption("na.action"), verbose=FALSE, tol=0.001, 
  max.iter=25, ...)

## Default S3 method:
boxTidwell(y, x1, x2=NULL, max.iter=25, tol=0.001, 
  verbose=FALSE, ...)
  
## S3 method for class 'boxTidwell'
print(x, digits=getOption("digits") - 2, ...)

Arguments

formula	two-sided formula, the right-hand-side of which gives the predictors to be transformed.
other.x	one-sided formula giving the predictors that are not candidates for transformation, including (e.g.) factors.
data	an optional data frame containing the variables in the model. By default the variables are taken from the environment from which boxTidwell is called.
subset	an optional vector specifying a subset of observations to be used.
na.action	a function that indicates what should happen when the data contain NAs. The default is set by the na.action setting of options.
verbose	if TRUE a record of iterations is printed; default is FALSE.
tol	if the maximum relative change in coefficients is less than tol then convergence is declared.
max.iter	maximum number of iterations.
y	response variable.
x1	matrix of predictors to transform.
x2	matrix of predictors that are not candidates for transformation.
...	not for the user.
x	boxTidwell object.
digits	number of digits for rounding.

Details

The maximum-likelihood estimates of the transformation parameters are computed by Box and Tidwell's (1962) method, which is usually more efficient than using a general nonlinear least-squares routine for this problem. Score tests for the transformations are also reported.

Value

an object of class boxTidwell, which is normally just printed.

Author(s)

John Fox [e-mail]

References

Box, G. E. P. and Tidwell, P. W. (1962) Transformation of the independent variables. Technometrics 4, 531-550.

Fox, J. (2016) Applied Regression Analysis and Generalized Linear Models, Third Edition. Sage.

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

Examples

boxTidwell(prestige ~ income + education, ~ type + poly(women, 2), data=Prestige)

car documentation built on Sept. 27, 2024, 9:06 a.m.