title: How to combine do.call() plot() and expression()
body: <p>I am getting an error when I try and combine using <code>expression</code> with <code>do.call</code> and <code>plot</code>. </p>
  
  <pre><code> x &lt;- 1:10
   y &lt;- x^1.5
  </code></pre>
  
  <p>I can get the plot I want by using only the <code>plot</code> function:</p>
  
  <pre><code>plot(y~x,xlab=expression(paste("Concentration (",mu,"M)")))
  </code></pre>
  
  <p>However, I would like to implement my plot using <code>do.call</code>. I have a really long list of parameters stored as a list, <code>p</code>. However, when I try and pass the list to <code>do.call</code> I get the following error:</p>
  
  <pre><code>p &lt;- list(xlab=expression(paste("Concentration (",mu,"M)")))
  do.call(plot,c(y~x,p))
  Error in paste("Concentration (", mu, "M)") : 
    object 'mu' not found
  </code></pre>
  
  <p>I also tried defining the formula explicitly in the args passed to <code>do.call</code>. ie. <code>do.call(plot,c(formula=y~x,p))</code>. I do not understand why I am getting the error - especially because the following does not give an error:</p>
  
  <pre><code>do.call(plot,c(0,p))
  </code></pre>
  
  <p>(and gives the desired mu character in the xaxis).</p>