How to change reference category in ordered logistic regression

[GerineLodder]

I have a variable with 5 levels.
Level 5 is now automatically taken as the reference category (that is: I get intercept_1 thru intercept_4), but I want level 1 to be the reference category (i.e., have intercept_2 thru intercept_5 estimated).
What code do I have to add to change that?

If this information is available in any documentation, I would be happy if you could point me to that info as well (So far, I have worked through the Zang et al. 2016 paper, the "translation" of chapter 13 about ordered logistic regression into R2mlwin and the LEMMA course material, although that doesn't include Rcode).

[ChrisCharlton]

To do this you can either use the R relevel() function (https://stat.ethz.ch/R-manual/R-devel/l ... level.html) as used at the beginning of http://www.bristol.ac.uk/cmm/media/r2ml ... rGuide10.R or you can specify the reference category in the model equation as in the section 11.4 A two-level model in http://www.bristol.ac.uk/cmm/media/r2ml ... rGuide11.R.

[GerineLodder]

Could you indicate where in the function of 11.4 the reference category is specified?

I have tried replacing:

Code: Select all

Function <- logit(variable, cons, 5) ~ 1 + (1[1:4] |school)  

With:

Code: Select all

Function <- logit(variable, cons, 5) ~ 1 + (1[2:5] |school)  

But that doesn't work.

[ChrisCharlton]

It's the third parameter of the logit() function. The three parameters are:

1. Response
2. Denominator
3. Reference category

Note that the category specified needs to be the underlying value if it is a factor variable.

[GerineLodder]

Thanks!! Thought the 5 was for "N categories", so good to know!