tran.family.box.cox {alr3}R Documentation

Compute transformation families

Description

These are internal functions that compute families of transformations. The user accesses these functions using powtran.

Usage

## S3 method for class 'box.cox'
tran.family(U, lambda, modified = TRUE)
## S3 method for class 'yeo.johnson'
tran.family(U,lambda,modified=TRUE) 
## S3 method for class 'power'
tran.family(U,lambda,modified=FALSE)

Arguments

U

The variable to be transformed. Missing values are permitted. U must be strictly positive unless family="yeo.johnson".

lambda

The transformation parameter, typically a value between -2 and 2.

modified

TRUE to divide by the Jacobian, as need to transform the response, FALSE for no division.

Details

Uses either the Box-Cox power family, the Yeo-Johnson generalization of this family for non-strictly-positive variables, or basic power transformations.

You can add additional families by writing a function tran.family.myfamily with the same arguments as tran.family.box.cox, and then set family="myfamily" in the call to powtran.

tran.family.YJ is an alias for tran.family.yeo.johnson. tran.family.boxcox is an alias for tran.family.box.cox. tran.family.basic is an alias for tran.family.power.

Value

Returns a vector of the same length as U with the transformed values.

Author(s)

Sanford Weisberg, sandy@stat.umn.edu

References

Weisberg, S. (2005). Applied Linear Regression, third edition. New York: Wiley, Chapter 7.

Yeo, In-Kwon and Johnson, Richard (2000). A new family of power transformations to improve normality or symmetry. Biometrika, 87, 954-959.

See Also

powtran.

Examples

data(ufcwc)
attach(ufcwc)
powtran(Height,lambda=0)

[Package alr3 version 1.1.12 Index]