Sorry --failed to cc the list. -- Bert On Fri, Apr 5, 2013 at 9:29 PM, Bert Gunter <bgun...@gene.com> wrote:
Have you tried plotting your data?! >library(lattice) >densityplot(yourdata) Forget tests of normality -- they are a BAD idea, despite what the statistics textbooks say (IMHO obviously) -- and focus on what the data are trying to tell you, which sure ain't that they are a sample from a normal distribution! Subject matter knowledge and problem context -- and probably explicit knowledge of how the data were produced -- are probably essential. -- Bert > > On Fri, Apr 5, 2013 at 3:47 PM, Beatriz González Domínguez > <aguitatie...@hotmail.com> wrote: >> Hi everybody, >> >> I would be very grateful if you could give me your thoughts on the following >> issue. >> >> I need to perform Box-Cox (bcPower€ ) transformation on my data. To do >> this, I calculated lambda using the function '€ powerTransform'€ . >> powerTransform(data) >> However, I got an error message when performing this function: >> Convergence failure: return code = 52 >> I was told by John Fox that the nature of my data was probably causing the >> problem so I applied the following transformation: >> powerTransform(1e7*(data - 0.99*(min(data)))) [1] >> And it worked! However, now when I try to check the normality of my data, >> shapiro.test(data) >> I get a new warning message: >> Error in shapiro.test(data) : >> ifault=6. This should not happen >> I think this may be solved by removing the transformation I applied >> previously in [1], but I’m not sure how to do it properly. >> >> Could anyone give me some advice? >> >> MY DATA: > c(0.000103113, 0.000102948, 0.000104001, 0.000103794, 0.000104628, > 9.2765e-05, 9.4296e-05, 9.5025e-05, 9.4978e-05, 9.8821e-05, 9.7586e-05, > 9.6285e-05, 0.00010158, 0.000100919, 0.000103535, 0.000103321, > 0.000102842, 0.000102315, 0.0001033, 0.000103691, 0.000102689, > 0.000103248, 0.000101216, 0.000103127, 0.000103439, 0.000102818, > 0.000103482, 0.00010227, 0.000104264, 0.000104672, 0.000104586, > 0.000104516, 0.000104585, 0.000103804, 0.000103702, 0.000103405, > 0.000104815, 0.000101718, 0.000101792, 0.000103273, 0.000102942, > 0.000102522, 0.000103149, 0.0001036995, 0.0001039735, 0.000101487666666667, > 0.000102796) >> >> Thanks a lot!! >> >> Bea >> >> >> >> >> [[alternative HTML version deleted]] >> >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > > > -- > > Bert Gunter > Genentech Nonclinical Biostatistics > > Internal Contact Info: > Phone: 467-7374 > Website: > http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
