title: How to make 3D plots with categorical data in R?
body: <p>I've been trying to create a 3D bar plot based on categorical data, but have not found a way.</p>
  
  <p>It is simple to explain. Consider the following example data (the real example is more complex, but it reduces to this), showing the relative risk of incurring something broken down by income and age, both categorical data.</p>
  
  <p>I want to display this in a 3D bar plot (similar in idea to <a href="http://demos.devexpress.com/aspxperiencedemos/NavBar/Images/Charts/ManhattanBar.jpg" rel="noreferrer">http://demos.devexpress.com/aspxperiencedemos/NavBar/Images/Charts/ManhattanBar.jpg</a>). I looked at the scatterplot3d package, but it's only for scatter plots and doesn't handle categorical data well. I was able to make a 3d chart, but it shows dots instead of 3d bars. There is no chart type for what I need. I've also tried the rgl package, but no luck either. I've been googling for more than an hour now and haven't found a solution. I have a copy of the ggplot2 - Elegant Graphics for Data Analysis book as well, but ggplot2 doesn't have this kind of chart.</p>
  
  <p>Is there another freeware app I could use? OpenOffice 3.2 doesn't have this chart either.</p>
  
  <p>Thank you for any hints.</p>
  
  <pre><code>Age,Income,Risk
  young,high,1
  young,medium,1.2
  young,low,1.36
  adult,high,1
  adult,medium,1.12
  adult,low,1.23
  old,high,1
  old,medium,1.03
  old,low,1.11
  </code></pre>