Data which are both positive and negative cannot be log transformed. Keep in mind that the purpose of transformation is to normalise the residuals, not to linearise the data. If you cannot find a transformation that normalises the residuals then there are techniques for dealing with the data, although whether you will find a black box to do this in SAS I don't know.
Bill Silvert ----- Original Message ----- From: "Sami Ullah" <[EMAIL PROTECTED]> To: <ECOLOG-L@LISTSERV.UMD.EDU> Sent: Tuesday, January 30, 2007 9:39 PM Subject: Log transformation of negative values in SAS?? > Hello Ecologers: > > I have a data set of N2O fluxes from forest soils in which some values are > positive and some negative. As the distribution in non-normal, I want to > log-transform the data. However, the log transformation command in SAS > transform positive values and ignores the negative. Can anyone guide me on > how to log-transform the data using SAS or anyother software to be able to > take care of both the positive and negative values. > > Thanks in anticipation. > > Sami Ullah > Department of Geography > McGill University, Canada > [EMAIL PROTECTED] > >
