title: How can I tell if event 1 occurred before, after or at the same time as event 2?
body: <p>New to R: If I have multiple observations for the same ID.  How can I tell if event 1 occurred before, after or at the same time as event 2 for each ID?</p>
  
  <p>ID is an integer. The number of observations for each ID varies.  Time is just the time period; 1,2,...t. Events 1 and 2 are 0/1 dummies.  </p>
  
  <p>I need to be able to count the number of times event 1 occurs before, after or at the same time as event 2.  Seems like this should be pretty simple/straight forward, but I haven't had any luck.  </p>
  
  <p>UPDATE: this should give a sense of the data:</p>
  
  <pre><code>my.df &lt;-  structure(list(ID = c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L, 
  3L, 3L), Time = c(1L, 2L, 3L, 4L, 1L, 2L, 3L, 1L, 2L, 3L, 4L, 
  5L), Event.1 = c(0L, 1L, 0L, 1L, 0L, 1L, 0L, 0L, 0L, 1L, 1L, 
  1L), Event.2 = c(1L, 0L, 0L, 0L, 0L, 1L, 1L, 1L, 1L, 1L, 0L, 
  0L)), .Names = c("ID", "Time", "Event.1", "Event.2"), class = "data.frame", row.names = c(NA, 
  -12L))
  </code></pre>
  
  <p>Thanks!</p>