[R] Scaling variables to positive values using scale() or performing BoxCox on negative data

[David Winsemius]

On Nov 30, 2009, at 11:02 AM, Henry Thorogood wrote:

> Hi,
>
> I'm doing some work with linear models, and I've scaled my data  
> using the
> scale(dataset) function. This was great at removing the skew, but I  
> now
> can't perform the Box Cox transformation on the data set (using the
> boxcox(dataset) function), as the scaling has returned negative  
> values.

Scaling (at least that using the default approach with that function)  
should not "remove" skewness.

>
> So my question is: how can I get the scale function to return a  
> positive set
> of data (so I can use Box-Cox),

You could shift the scaled values to the right.

> or how can I get the boxcox function to
> handle negative values.

Which boxcox function? And have you looked at all of its available  
parameters?

-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT