Hello everyone,

I have a variable with several categories and I want to convert this  
into dummy variables and do logistic regression on it. I used  
model.matrix to create dummy variables but it always picked the  
smallest one as the reference. For example,

model.matrix(~.,data=as.data.frame(letters[1:5]))

will code 'a' as '0 0 0 0'. But I want to code another category as  
reference, say 'b'. How to do it in R using model.matrix? Is there  
other way to do it if model.matrix  has no such functionality?

Thanks!



	[[alternative HTML version deleted]]

