title: Double box plots in ggplot2
body: <p>I want to describe the distributions of two variables using box plots spanning both the x and y axes. </p>
  
  <p>The site <a href="https://tomizonor.wordpress.com/2013/03/15/double-box-plot/" rel="noreferrer">linked here</a> has some nice examples (below) and it has package using base plot - <a href="https://cran.r-project.org/web/packages/boxplotdbl/index.html" rel="noreferrer">boxplotdbl</a>. </p>
  
  <p>I was wondering if a similar plot was possible in <code>ggplot2</code>. Using the figure below as an example and the <code>iris</code> data, how can I plot the box plot of <code>Sepal.Length</code> and <code>Sepal.Width</code> and color by <code>Species</code>? </p>
  
  <p><a href="https://i.stack.imgur.com/u1MsD.png" rel="noreferrer"><img src="https://i.stack.imgur.com/u1MsD.png" alt="enter image description here"></a></p>
  
  <p>I was surprised to see that following code is close, but would like the whiskers, rather than the box, to be extended along the x-axis.</p>
  
  <pre><code>library(ggplot2)
  ggplot(iris) + 
    geom_boxplot(aes(x = Sepal.Length, y = Sepal.Width, fill = Species), alpha = 0.3) +
    theme_bw()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/j7S35.png" rel="noreferrer"><img src="https://i.stack.imgur.com/j7S35.png" alt="enter image description here"></a></p>