Oliver, I am attaching an HTML document in which I have plotted -2Log(x) vs. x. If you examine the plot you will see that -2Log(x) can be negative. Since -2Log(x) is part of AIC and BIC, AIC and BIC can be negative. John
John Sorkin M.D., Ph.D. Chief, Biostatistics and Informatics Baltimore VA Medical Center GRECC, University of Maryland School of Medicine Claude D. Pepper OAIC, University of Maryland Clinical Nutrition Research Unit, and Baltimore VA Center Stroke of Excellence University of Maryland School of Medicine Division of Gerontology Baltimore VA Medical Center 10 North Greene Street GRECC (BT/18/GR) Baltimore, MD 21201-1524 (Phone) 410-605-7119 (Fax) 410-605-7913 (Please call phone number above prior to faxing) [EMAIL PROTECTED] >>> "Hannu Kahra" <[EMAIL PROTECTED]> 09/07/07 4:32 AM >>> Olivier, type ?AIC and have a look at the description Description: Generic function calculating the Akaike information criterion for one or several fitted model objects for which a log-likelihood value can be obtained, according to the formula -2*log-likelihood + k*npar, where npar represents the number of parameters in the fitted model, and k = 2 for the usual AIC, or k = log(n) (n the number of observations) for the so-called BIC or SBC (Schwarz's Bayesian criterion). AIC = -2*log-likelihood + k*npar can be negative as SBC, too. Hannu On 9/7/07, Olivier MARTIN <[EMAIL PROTECTED]> wrote: > > Hi all, > > > I obtained negative values for AIC and BIC criteria for a particular > model that I have > developped... > > I don't remember to have negative values for these crietria for others > applications, so I am a > little suprised... Could anyone tell me if something is wrong or his > conclusion concerning my model? > > Best regards, > Olivier. > > ______________________________________________ > 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 > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code. Confidentiality Statement: This email message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message.
y = -2Log[x] Out[20]= -2 Log[x] In[22]:= RowBox[{Plot, [, RowBox[{y, ,, RowBox[{{, RowBox[{x, ,, 0.01, ,, 4}], }}], ,, AxesLabel {x, -2Log[x]}}], ]}] [Graphics:HTMLFiles/-2Log_10.gif] Out[22]= -Graphics- ______________________________________________________________________ Created by [1]Mathematica (September 7, 2007) References 1. http://www.wolfram.com/
______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.