title: R aggregate a dataframe by hours from a date with time field
body: <p>I'm relatively new to R but I am very familiar with Excel and T-SQL. </p>
  
  <p>I have a simple dataset that has a date with time and a numeric value associated it. What I'd like to do is summarize the numeric values by-hour of the day. I've found a couple resources for working with time-types in R but I was hoping to find a solution similar to is offered excel (where I can call a function and pass-in my date/time data and have it return the hour of the day).</p>
  
  <p>Any suggestions would be appreciated - thanks!</p>