title: Hourly time series plotting
body: <p>I'm trying to plot the following hourly data. How can I change my data to an time series object? Was trying with the <code>xts</code> package but got an error message:</p>
  
  <pre><code>new_data &lt;- structure(list(starttime = c("01.01.2015 00:00", "01.01.2015 01:00", 
  "01.01.2015 02:00", "01.01.2015 03:00", "01.01.2015 04:00", "01.01.2015 05:00"
  ), Fossil = c(435, 434, 435, 436, 436, 436)), .Names = c("starttime", 
  "Fossil"), row.names = c(NA, -6L), class = "data.frame")
  
  str(new_data)
  
  $ starttime: chr  "01.01.2015 00:00" "01.01.2015 01:00" "01.01.2015 02:00"  "01.01.2015 03:00" ...
  $ Fossil   : int  435 434 435 436 436 436 434 436 415 331
  
   head(new_data)
   starttime         Fossil
  1 01.01.2015 00:00    435
  2 01.01.2015 01:00    434
  3 01.01.2015 02:00    435
  4 01.01.2015 03:00    436
  5 01.01.2015 04:00    436
  6 01.01.2015 05:00    436
  
  hnew_dataxts &lt;- as.xts(x=new_data[,"Fossil"], order.by=new_data[,"starttime"])
  colenames(hnew_dataxts) &lt;- colnames(new_data)[-1]
  
      Error in xts(x, order.by = order.by, frequency = frequency, .CLASS = "integer",  : 
  order.by requires an appropriate time-based object
  </code></pre>