title: Plotting time (HMS) with ggplot2
body: <p>I'm trying to plot a running sessionsI want to make a ggplot with:
  x=distance (2.2KM, 5KM, 10KM , 12.8KM, Ziel)
  Y= time (HMS)</p>
  
  <p>I have the following data:</p>
  
  <pre><code>'data.frame':   16333 obs. of  6 variables:
   $ Numéro  : chr  "6526" "5427" "6528" "6529" ...
   $ X2.2km  : chr  "00:10:47.4" "00:08:58.2" "00:11:10.4" "00:09:27.3" ...
   $ X5km    : chr  "00:26:05.0" "00:21:46.1" "00:27:13.5" "00:22:35.3" ...
   $ X10km   : chr  "00:56:30.1" "00:45:59.3" "00:58:53.1" "00:47:51.7" ...
   $ X12.8km : chr  "01:14:24.7" "00:59:50.7" "01:17:35.0" "01:01:42.6" ...
   $ Zielzeit: chr  "01:37:40.0" "01:16:38.1" "01:41:53.0" "01:19:02.5" ...
  </code></pre>
  
  <p>the next step is to use  <strong>melt</strong> function from library <strong>reshape2</strong> and <strong>lubridate</strong></p>
  
  <pre><code>xx&lt;-melt(xx,id="Numéro")
  ####Using lubridate ####
  xx$value&lt;-hms(xx$value)
  </code></pre>
  
  <p>My problem is here when i try to plot simple graphics, i receive the following message</p>
  
  <pre><code>&gt; ggplot(xx,aes(variable,value))+geom_point()
  Error in x &lt; range[1] : cannot compare Period to Duration:
   coerce with 'as.numeric' first.
  &gt; ggplot(xx,aes(variable,value))+geom_line()
  Error in x &lt; range[1] : cannot compare Period to Duration:
   coerce with 'as.numeric' first.)
  </code></pre>
  
  <p>DATASET</p>
  
  <pre><code>  xx &lt;- read.table(header=TRUE, text="   
         Numéro variable value
    1    6526   X2.2km 10M 47.4S
    2    5427   X2.2km  8M 58.2S
    3    6528   X2.2km 11M 10.4S
    4    6529   X2.2km  9M 27.3S
    5    6530   X2.2km  8M 29.3S")
  </code></pre>
  
  <p>Thank for any kind of contributions .</p>