need help with errors in betareg analysis
knussear wrote:
Yes, fair enough. I wasn't sure it was fitting the mode at all, but here is an example of what I see
model <- betareg(ACT ~ ST+DOY, data = actDL_F)
Warning messages: 1: In sqrt(diag(fisherinv)) : NaNs produced 2: In sqrt(diag(fisherinv)) : NaNs produced 3: In sqrt(W) : NaNs produced 4: In sqrt(W) : NaNs produced 5: In sqrt(1 + phihat) : NaNs produced Call: betareg(formula = ACT ~ ST + DOY, data = actDL_F) Coefficients: (Intercept) ST DOY phi 1.780e+07 -1.149e+09 2.225e+08 -4.090e+08 So I don't see a W listed, but the phi is going negative just as you suggested. So are the results wonky if phi is negative?
These results are definitely wonky -- look at the orders of magnitude ... I don't know what to suggest at this point without further details of the data. You could try another package that is also capable of doing beta regression (bbmle will do it, albeit less efficiently and in a less canned way than betareg), but I suspect there's something funny about the data (that doesn't show up in the summaries) -- have you checked it graphically? Ben Bolker
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