title: Regression in R using poly() function
body: <p>The function poly() in R is used in order to produce orthogonal vectors and can be helpful to interpret coefficient significance. However, I don't see the point of using it for prediction. To my view, the two following model (model_1 and model_2) should produce the same predictions.</p>
  
  <pre><code>q=1:11
  v=c(3,5,7,9.2,14,20,26,34,50,59,80)
  model_1=lm(v~poly(q,2))
  model_2=lm(v~1+q+q^2)
  predict(model_1)
  predict(model_2)
  </code></pre>
  
  <p>But it doesn't. Why?</p>