title: how to make sure the odds.ratio when the predictor is changed?
body: <p>I met a problem. I calculate the odd.raio by using glm. </p>
  
  <p>When the predictor outcomes were "A" and "B",respectively, the odd.ratio value is 0.88. However, outcome was "C" and "B", the odd.ratio value is 1.127948.</p>
  
  <p>I don't know what the difference between "AB" and "BC" in the glm. the character can affect the results of odd.ratios 
   which is right?</p>
  
  <p>example code</p>
  
  <pre><code> outcome &lt;- as.factor(c(rep("C",30),rep("B",28)))
   #outcome &lt;- as.factor(c(rep("A",30),rep("B",28)))
  a &lt;- c(seq(1,30,1),seq(1,28,1))
  glm.log &lt;- glm(outcome ~ scale(a), control = list(maxit = 50), family =              binomial(link = "logit"))
  res &lt;- summary(glm.log)$coefficients[2, 1:2]
  odd.ratio &lt;- exp(res[1])
  print(odd.ratio)
  </code></pre>