title: What does group do in geom_bar function in R?
body: <p>These are from <em><a href="http://r4ds.had.co.nz/" rel="nofollow noreferrer">R for data Science</em> book</a></p>
  
  <pre><code>ggplot(data = demo) +
    geom_bar(mapping = aes(x = cut, y = freq), stat = "identity")
  </code></pre>
  
  <p>What does <code>stat = "Identity"</code> do?</p>
  
  <pre><code>ggplot(data = diamonds) + 
    geom_bar(mapping = aes(x = cut, y = ..prop.., group = 1))
  </code></pre>
  
  <p>What does <code>group = 1</code> do? I didnt find a difference even when I put group = 0, 2, ... etc.</p>