title: Correctly set R default graphic device to quartz?
body: <p>I tried to add the following line in my <code>.Rprofile</code> file:</p>
  
  <pre><code>options(device = quartz)
  </code></pre>
  
  <p>It produced an error: </p>
  
  <pre><code>Error in options(device = quartz) : object 'quartz' not found
  </code></pre>
  
  <p>Then I tried:</p>
  
  <pre><code>options(device = "quartz")
  </code></pre>
  
  <p>And it works.</p>
  
  <p>However, both work in the regular <code>R</code> session. Can anyone tell me what is the reason for the difference in behavior? </p>