So I've built a MLR model in R, it has a categorical variable in it with like 93 levels (so many). I tried grouping some levels or removing the predictor altogether but this had a negative impact so I've had to leave it in. Model seems to be working fine so I want to created a predicted vs observed plot, however when I run the predict function on my model it comes up with this error:
"Error in model.frame.default(Terms, newdata, na.action = na.action, xlev = object$xlevels) : factor C has new levels xxxx, yyyy"
Has anyone had this error before? I'm not sure how to fix it, and it only comes up when I try to predict.
Here's the code I used also:
lm12<-lm(log(A)~B+C+log(D)+E+F+log(G)+log(H), data=mydata)
pred<-predict(lm12,mydata)
(B and C are categorical, the rest are continuous.)
Thank you!