title: forward stepwise regression
body: <p>In R stepwise forward regression, I specify a minimal model and a set of variables to add (or not to add):</p>
  
  <pre><code>min.model = lm(y ~ 1)
  fwd.model = step(min.model, direction='forward', scope=(~ x1 + x2 + x3 + ...))
  </code></pre>
  
  <p>Is there any way to specify using all variables in a matrix/data.frame, so I don't have to enumerate them?</p>
  
  <p>Examples to illustrate what I'd like to do, but they don't work:</p>
  
  <pre><code># 1
  fwd.model = step(min.model, direction='forward', scope=(~ ., data=my.data.frame))
  
  # 2
  min.model = lm(y ~ 1, data=my.data.frame)
  fwd.model = step(min.model, direction='forward', scope=(~ .))
  </code></pre>