title: x-axis in boxplot in R
body: <p>I hope that with this edition my question improve and it could be reproducible.</p>
  
  <p>Imagine I have this data, in which X are certain values of a measure and Y are 4 groups, each one representing forage quality. I could used letters for the forage quality, as L (low), M (medium), H (high) and VH (very high), but I use the values because I want the boxplots to be drawn in the x-axis at this real points, 4.8, 13, 18.02 and 21, and not with the same distance between them. </p>
  
  <pre><code>    Data &lt;- data.frame(X = sample(1:12),
      Y = sample(rep(c(4.8, 13, 18.02, 21), each=3)))
  </code></pre>
  
  <p>I use this simple code to draw the boxplot</p>
  
  <pre><code>    boxplot(Data$X ~ Data$Y)
  </code></pre>
  
  <p>How could I scale the boxplots along the x-axis? Should I use any graphic library instead?</p>
  
  <p>Thanks</p>