Example for Box-Cox

Load the Library and Data, Plot

library(car)

## Warning: package 'car' was built under R version 4.0.5

## Loading required package: carData

library(ResourceSelection)

## Warning: package 'ResourceSelection' was built under R version 4.0.5

## ResourceSelection 0.3-5   2019-07-22

mytrees=trees #for use with transformation
kdepairs(trees)

Conduct the Transformation

(myt=powerTransform(as.matrix(mytrees)~1))

## Estimated transformation parameters 
##      Girth     Height     Volume 
## -0.1994186  1.4786133 -0.1191381

testTransform(myt, myt$lambda) #performs likelihood ratio test for transformation, Ho:  Not different from multivariate normal

##                                     LRT df pval
## LR test, lambda = (-0.2 1.48 -0.12)   0  3    1

Apply the Transformation and Evaluate

for (i in 1:3) mytrees[,i]=mytrees[,i]^myt$lambda[i]
kdepairs(mytrees)