How to calculate the difference between dates in R for each unique id
<p>I am new to R and have the following data of user name and their usage date for a product (truncated output):</p>

<pre><code>Name,  Date 
Jane,  01-24-2016 10:02:00
Mary,  01-01-2016 12:18:00
Mary,  01-01-2016 13:18:00
Mary,  01-02-2016 13:18:00
Jane,  01-23-2016 10:02:00
</code></pre>

<p>I would like to do some analysis on difference between <code>Date</code>, in particular the number of days between usage for each user. I'd like to plot a histogram to determine if there is a pattern among users.</p>

<ol>
<li>how do I compute the difference between dates for each user in R ? </li>
<li>are there any other visualizations besides histograms I should explore ?</li>
</ol>

<p>Thanks</p>