boxcoxR: Transform data using a boxcox transformation
Description
This function takes a variable as input, computes the optimal lambda
using a boxcox transformation, then returnes a transformed version of the variable.
Usage
boxcoxR(x, minval = 0.01, lam = F, ...)
Arguments
x
a numerical vector
minval
before a transformation is performed, the variables must often be positive. This tells R what the minimum value should be. Defaults to .01.
lam
Should the lambda value be returned?
...
additional parameters to be used in the model fitting.
Details
The MASS package has a function that computes the optimal lambda value for a particular regression equation. However, it currently (as of version 7.3-23)
returns a lambda vector rather than the boxcox transformed variable. This function is a wrapper for boxcox that actually returns a vector that is a
transformed version of the original variable.
References
Venables, W. N. & Ripley, B. D. (2002) Modern Applied Statistics with S. Fourth Edition. Springer, New York. ISBN 0-387-95457-0
x = rnorm(100)^2### use original boxcox functionboxcox(x~1, plot=FALSE) ## returns a vector of lambda values and their likelihoods### use boxcoxR functionboxcoxR(x)