caret (version 5.13-037)

BoxCoxTrans.default: Box-Cox Transformations

Description

This class can be used to estimate a Box-Cox transformation and apply it to existing and future data

Usage

BoxCoxTrans(y, ...)
## S3 method for class 'default':
BoxCoxTrans(y, x = rep(1, length(y)), 
            fudge = 0.2, numUnique = 3, na.rm = FALSE, ...)
## S3 method for class 'BoxCoxTrans':
predict(object, newdata, ...)

Arguments

y

a strictly positive numeric vector of data to be transformed

x

an optional dependent variable to be used in a liner model

fudge

a tolerance value: lambda values within +/-fudge will be coerced to 0 and within 1+/-fudge will be coerced to 1

numUnique

how many unique values should y have to estimate the transformation?

na.rm

a logical value indicating whether NA values should be stripped from y and x before the computation proceeds.

...

for BoxCoxTrans: options ot pass to boxcox. plotit should not be passed through. For predict.BoxCoxTrans, additional arguments are ignored.

object

an object of class BoxCoxTrans

newdata

a numeric vector of values to transform

Value

• BoxCoxTrans returns a list of class BoxCoxTrans with elements
• lambda
  estimated transformation value
• fudge
  value of fudge
• n
  number of data points used to estimate lambda
• summary
  the results of summary(y)
• ratio
  max(y)/min(y)
• skewness
  sample skewness statistic
• predict.BoxCoxTrans returns a numeric vector of transformed values

Details

This function is basically a wrapper for the boxcox function in the MASS library. It can be used to estimate the transformation and apply it to new data.

If any(y <= 0)<="" code=""> or if length(unique(y)) < numUnique, lambda is not estimated and no transformation is applied.

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.

See Also

boxcox, preProcess

Examples

data(BloodBrain)

ratio <- exp(logBBB)
bc <- BoxCoxTrans(ratio)

bc

predict(bc, ratio[1:5])


ratio[5] <- NA
bc2 <- BoxCoxTrans(ratio, bbbDescr$tpsa, na.rm = TRUE)
bc2