title: Plot dates on the x axis and time on the y axis with ggplot2
body: <p>I have read in a series of 37 dates and times that an event happened. It is now sitting as a POSIXlt object. I want a graphic representation of the times that the events happened on each day. So the x axis should be the date and y axis should be the time of day.</p>
  
  <p>then I tried to plot it with ggplot2</p>
  
  <pre><code>qplot(day(dttm), hour(dttm))
  </code></pre>
  
  <p>That is kind of what I want but it does not have the resolution of minutes. How do I have hours and minutes included in the y axis?</p>
  
  <p>Here is some sample data</p>
  
  <pre><code>dttm
   [1] "2011-11-16 10:39:20" "2011-11-16 10:56:32" "2011-11-16 11:52:43" "2011-11-16 12:10:42"
   [5] "2011-11-16 13:10:13" "2011-11-16 13:41:10" "2011-11-16 13:48:07" "2011-11-16 14:54:04"
   [9] "2011-11-17 07:05:23" "2011-11-17 07:34:24" "2011-11-17 07:53:01" "2011-11-17 07:57:04"
  [13] "2011-11-17 08:09:16" "2011-11-17 08:23:43" "2011-11-17 10:20:54" "2011-11-17 10:45:13"
  [17] "2011-11-17 10:49:32" "2011-11-17 11:16:08" "2011-11-17 11:24:05" "2011-11-17 11:50:11"
  [21] "2011-11-17 11:52:47" "2011-11-17 11:54:42" "2011-11-17 11:55:25" "2011-11-17 11:57:34"
  [25] "2011-11-17 12:06:15" "2011-11-17 12:08:05" "2011-11-17 12:08:33" "2011-11-17 12:30:13"
  [29] "2011-11-17 13:24:41" "2011-11-17 13:44:41" "2011-11-17 13:48:55" "2011-11-17 14:59:08"
  [33] "2011-11-18 06:46:17" "2011-11-18 07:52:50" "2011-11-18 08:31:22" "2011-11-18 08:33:43"
  [37] "2011-11-18 08:50:08"
  </code></pre>
  
  <p>Here is the dput file</p>
  
  <pre><code>structure(list(sec = c(20, 32, 43, 42, 13, 10, 7, 4, 23, 24, 
  1, 4, 16, 43, 54, 13, 32, 8, 5, 11, 47, 42, 25, 34, 15, 5, 33, 
  13, 41, 41, 55, 8, 17, 50, 22, 43, 8), min = c(39L, 56L, 52L, 
  10L, 10L, 41L, 48L, 54L, 5L, 34L, 53L, 57L, 9L, 23L, 20L, 45L, 
  49L, 16L, 24L, 50L, 52L, 54L, 55L, 57L, 6L, 8L, 8L, 30L, 24L, 
  44L, 48L, 59L, 46L, 52L, 31L, 33L, 50L), hour = c(10L, 10L, 11L, 
  12L, 13L, 13L, 13L, 14L, 7L, 7L, 7L, 7L, 8L, 8L, 10L, 10L, 10L, 
  11L, 11L, 11L, 11L, 11L, 11L, 11L, 12L, 12L, 12L, 12L, 13L, 13L, 
  13L, 14L, 6L, 7L, 8L, 8L, 8L), mday = c(16L, 16L, 16L, 16L, 16L, 
  16L, 16L, 16L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 
  17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 
  17L, 18L, 18L, 18L, 18L, 18L), mon = c(10L, 10L, 10L, 10L, 10L, 
  10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 
  10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 10L, 
  10L, 10L, 10L, 10L, 10L, 10L), year = c(111L, 111L, 111L, 111L, 
  111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 
  111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 
  111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L, 111L
  ), wday = c(3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 
  4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
  4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L), yday = c(319L, 319L, 319L, 319L, 
  319L, 319L, 319L, 319L, 320L, 320L, 320L, 320L, 320L, 320L, 320L, 
  320L, 320L, 320L, 320L, 320L, 320L, 320L, 320L, 320L, 320L, 320L, 
  320L, 320L, 320L, 320L, 320L, 320L, 321L, 321L, 321L, 321L, 321L
  ), isdst = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 
  0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 
  0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L)), .Names = c("sec", "min", 
  "hour", "mday", "mon", "year", "wday", "yday", "isdst"), class = c("POSIXlt", 
  "POSIXt"))
  </code></pre>