On Sun, 9 Jan 2005, may sawasdee wrote:
Dear R-Help
I 'm using GLM function to Modelling. But when I used Gamma Family in GLM, then I can't run. It was error
glm(DamageRatio~MinTEMP+MaxTEMP+DayRain+Group1+Group2+Group3+Year,family=Gamma())Error in eval(expr, envir, enclos) : Non-positive values not allowed for the gamma family
Can Gamma Distribution use data begin 0 ?
No, That is an impossible value from a gamma distribution: see ?dgamma and note what it says about x.
and then when I used GLM in S-Plus Program then it done, but it didn't have AIC value.
Last Question why are not the AIC in R and S-plus equal.
You have just said S-Plus does not have an AIC value.! However, since a gamma GLM is not fitted by ML, you cannot get AIC from a glm fit unless you specify the dispersion (unlikely). Did you notice what ?glm says about the aic component? See also ?logLik.
-- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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