After reading a good amount of the answered questions on interpreting Beta Regression results (Best explanation here) and reading through the Betareg vignette, I still feel a lack of confidence writing my interpretations into my thesis. Just a bit of background first: I ran the following code, which by default uses a logit link:
betaMod <- betareg(BEVMarketShare ~ CumulFastStations + CumulNormalStations + IncentAvail + ModelsAvail + Price + Range + TechRatio + FuelPrices , data= OutliersRemoved)
Here's a small sample of my data:
Here are the results:
Let's take CumulFastStations for example, where the coefficient is 0.004756. If I use the interpretation I've come to understand best, for every additional Fast Charging Station added in a Bundesland you would expect relative change in the BEV Market Share by 4% in E(BEVMarketShare) / (1−E(BEVMarketShare)). So whether or not this is correct, I feel a bit strange repeating this for the various regressors I'd like to make predictions for. I've seen that it's also possible to use the predict function, but I'm having trouble figuring out why this code results in the error "Error in eval(predvars, data, env) : object 'CumulNormalStations' not found":
Test <- data.frame(CumulFastStations = seq(0, 300, by = 25)) Test$BEVMarketShare <- predict(betaMod, newdata = Test) print(Test) plot(BEVMarketShare ~ CumulFastStations, data = Test, type = "b")
My other question is possibly nonsense. I preformed regression on the same model above, however with the DV BEVMarketshare logit transformed:
logitvar_model <- lm(logit(BEVMarketShare) ~ CumulFastStations + CumulNormalStations + ModelsAvail + Range + TechRatio + FuelPrices, data = OutliersRemoved)
I'm only doing this to try to replicate the method used by one relevant study to my topic. The screenshot of the where the author notes his method seems to clearly indicate he performed a logit transformation on the DV.
So now I'm again confused on how to interpret the coefficients. I've only found information on logit regression, but not for a transformation with logit on the DV such as this .
I hope this isn't too much to digest, but I'm really kind of stuck with these two issues. Thank you very much in advance!