Re: [R] nlme questions (e.g., specifying group membership, changing options)

Are your categorical variables factors or ordered factors? If yes, lm and many other functions including, I believe, nlme, will automatically create the required dummy variables using contrasts specified by options()$contrasts. Consider the following: > options("contrasts") $contrasts

[R] nlme questions (e.g., specifying group membership, changing options)

I'm trying to better understand the nlme package and have a few questions. 1.) Other than using various coding strategies (e.g., dummy coding, effect coding), is there a way to identify group membership (i.e., treatment) directly? For example, the following code will fit a two group logist