Greetings, Carla: While it is possible to map any proper density into a normal through their CDFs, that may not be useful in your case.
I suggest that you first plot your data. ?qqnorm (Type ?qqnorm on the R command line and hit Enter.) Are your data continuous, or do they occur in groups? Do the data curve? Do they look like two (or more) distinct lines? If your data have only one mode and if they are smooth then the Box-Cox transform should provide a symmetrical result. Not all symmetrical densities are normal, of course. And if your data are discrete then using a continuous density like the normal (or Johnson family) is inappropriate. The purpose of "fitting" a distribution to data is usually to permit some probability statement, like Prob(x < X) = alpha. Why do you want to use the Johnson family? I am not aware of convenient methods for making such probability statements for them. Best wishes. Charles Annis, P.E. [EMAIL PROTECTED] phone: 561-352-9699 eFax: 614-455-3265 http://www.StatisticalEngineering.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, January 20, 2005 10:16 AM To: r-help Subject: [R] Johnson transformation Hello, I'm Carla, an italian student, I'm looking for a package to transform non normal data to normality. I tried to use Box Cox, but it's not ok. There is a package to use Johnson families' transormation? Can you give me any suggestions to find free software as R that use this trasform? Thank yuo very much Carla ____________________________________________________________ 6X velocizzare la tua navigazione a 56k? 6X Web Accelerator di Libero! Scaricalo su INTERNET GRATIS 6X http://www.libero.it ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
