title: Plot histograms over factor variables
body: <p>I'm trying to replicate the graph similar to the following (originally found <a href="http://37signals.com/svn/posts/3019-the-rhythms-of-37signals" rel="noreferrer">HERE</a>)<br>
  <img src="https://i.stack.imgur.com/bcjab.png" alt="stacked histograms"></p>
  
  <p>It's conceptually simple, but I'm a bit stumped as to how to do it in R. <br>
  To summarize: I want to generate histograms of behavioral frequency over the 24 hours of the day (24-level factor variable) by each day of the week. Then, I want to stack these histograms on top of each other so that the distribution of behavior over the hour of day can easily be compared (again, see example).</p>
  
  <p>For example, my data might look like this: </p>
  
  <pre><code>  weekday hour    count
    Tuesday   15      553
     Monday    1       53
     Monday   10      539
     Monday   15      629
    Tuesday    9      281
   Saturday    4       11
     Monday    3       20
     Sunday    3       10
     Sunday    7        2
     Sunday    2       17
  </code></pre>
  
  <p>How do I go about implementing the graph in the link above? I'm terrible with <code>ggplot</code>, but have a sense it's the likely solution.
  Thanks!</p>