title: How to re-level factor in ordinal logistic regression model in R?
body: <p>I am currently working on an ordinal logistic regression model with R. The output coefficients are using the same reference level. I am wondering how can I change the reference level? Be more specific, see the example below. I do not want to use real data, so I simulated one. Both a and T are from 1 to 5</p>
  
  <pre><code>polr(formula = T ~ a, data = d, Hess = TRUE)
  
  Coefficients:
        Value Std. Error  t value
  a2  0.18823     0.5734  0.32825
  a3  0.14747     0.5287  0.27895
  a4 -0.50157     0.5766 -0.86985
  a5  0.02843     0.5448  0.05219
  </code></pre>
  
  <p>The coefficient of "a" use reference level 1, a2, a3, a4, and a5 basically compare level 2,3,4,5 with reference level 1. My question is how can I relevel it so that the output will give a3|2, a4|3, a5|4(i.e. the beta3-beta2,beta4-beta3) automatically? I have search around and didn't find similar question. Thanks a lot. </p>