<p>I have a question about the <code>mice</code> package in R for multiple imputation. It is giving me an error message that I don't understand and have not been able to find information about so far on the internet. The error only occurs when I include a categorical variable with more than 2 levels with imputation method <code>polyreg</code>, so I wondered if I should ask here or on stackoverflow ? Frankly I prefer to ask here if possible because people here seem a bit more friendly !</p>

<p>Also, I'm slightly concerned about asking because ideally I would like to make a reproducable example, but there is a lot of data, plus the code, plus the predictor matrix, and the fact that my school probably would not be happy if I posted the data they gave me for private study on the internet. I suppose I could try to modify the data in slight ways to get around the last point. Is there any guidance for making examples (including how/where to post the data) ? Is it necessary to do make a working example ?  Could I just ask the question first (maybe some experts know the answer off the top of their heads) with the proviso that I will make an working example if requested (and given some guidance for doing so). </p>

<p>Sorry for the long posting !</p>
