title: Find predictors in lm object R
body: <p>I have a linear model in R</p>
  
  <pre><code> x &lt;- lm(dist ~ poly(speed, degree=2), data = cars)
  </code></pre>
  
  <p>and want to find out, </p>
  
  <p>a) which variables of cars are used as predictors in the model. Here: "speed" </p>
  
  <p>b) how to access them in the model object. Here:  4  4  7  7  8  9 10 ...</p>
  
  <p>model.frame contains the already transformed terms and does not help. The lm object contains the data, as expand.model.frame(x, ~ speed) does work. But where is it? </p>
  
  <p>Any hints?</p>