title: Plotting quantile regression by variables in a single page
body: <p>I am running quantile regressions for several independent variables separately (same dependent). I want to plot only the slope estimates over several quantiles of each variable in a single plot. </p>
  
  <p>Here's a toy data:</p>
  
  <pre><code>set.seed(1988)
  
  y &lt;- rnorm(50, 5, 3)
  x1 &lt;- rnorm(50, 3, 1)
  x2 &lt;- rnorm(50, 1, 0.5)
  
  # Running Quantile Regression 
  require(quantreg)
  fit1 &lt;- summary(rq(y~x1, tau=1:9/10), se="boot")
  fit2 &lt;- summary(rq(y~x2, tau=1:9/10), se="boot")
  </code></pre>
  
  <p>I want to plot only the slope estimates over quantiles. Hence, I am giving <code>parm=2</code> in <code>plot</code>.</p>
  
  <pre><code> plot(fit1, parm=2)
   plot(fit2, parm=2)
  </code></pre>
  
  <p>Now, I want to combine both these plots in a single page.</p>
  
  <p>What I have tried so far;</p>
  
  <ol>
  <li>I tried setting <code>par(mfrow=c(2,2))</code> and plotting them. But it's producing a blank page. </li>
  <li>I have tried using <code>gridExtra</code> and gridGraphics without success. Tried to convert base graphs into Grob objects as stated <a href="https://stackoverflow.com/a/33848995/3766430">here</a></li>
  <li>Tried using function <code>layout</code> function as in <a href="http://seananderson.ca/courses/11-multipanel/multipanel.pdf" rel="nofollow noreferrer">this</a> document</li>
  <li>I am trying to look into the source code of <code>plot.rqs</code>. But I am unable to understand how it's plotting confidence bands (I'm able to plot only the coefficients over quantiles) or to change <code>mfrow</code> parameter there.</li>
  </ol>
  
  <p>Can anybody point out where am I going wrong? Should I look into the source code of <code>plot.rqs</code> and change any parameters there?</p>