title: Is there a way to change the way R labels the interaction parameter in model output?
body: <p>I am having a seemingly simple but very frustrating problem. When you run a model with an interaction term in R, R names the parameter generated "var1:var2" etc. Unfortunately, this naming convention prevents me from calculating predicted values and CI's where newdata is required, because  ":" is not a character that can be included in a column header, and the names in the original data frame must exactly match those in newdata. Has anyone else had this problem?</p>
  
  <p>Here is a sample of my code:</p>
  
  <pre><code>wemedist2.exp = glm(survive/trials ~ sitedist + type + sitedist*type + roaddist, family =          binomial(logexp(wemedata$expos)), data=wemedata)
  summary(wemedist2.exp)
  wemepredict3 = with(wemedata, data.frame(sitedist=mean(sitedist),roaddist=mean(roaddist),    type=factor(1:2))) 
  wemepredict3 = cbind(wemepredict3, predict(wemedist2.exp, newdata = wemepredict3, type = "link", se = TRUE))
  </code></pre>
  
  <p>This produces a table with predicted values for each of the variables at the specified levels, but not interaction.</p>