title: create timeseries based on start and end date
body: <p>I have two columns of data, one of timestamp in 'yyyy-mm-dd hh:mm:ss' format and another numeric column with number of orders.</p>
  
  <p>How can I define an hourly time series of the 'no of orders' column with a start date &amp; end date.</p>
  
  <p>I tried the below code but got the error '<strong>invalid time series parameters specified</strong>'</p>
  
  <pre><code>OFS_ts &lt;-ts(data = temp$OFS_transformed,start = temp$DateHour[1],end = temp$DateHour[nrow(temp)])
  </code></pre>
  
  <p>OFS_transformed -> number of sales orders at that time-stamp (the data to be converted into time series )</p>
  
  <p>DateHour -> timestamp in the format '2015-10-25 18:00:00'</p>
  
  <p>temp -> dataset</p>
  
  <pre><code>OFS_transformed    DateHour
  
  6.89871446      2015-10-30 00:00:00
  6.1548579376    2015-10-30 01:00:00
  5.9889612322    2015-10-30 02:00:00
  6.678342022     2015-10-30 03:00:00
  5.7333410385    2015-10-30 04:00:00
  6.8741984193    2015-10-30 05:00:00
  5.4806386163    2015-10-30 06:00:00
  </code></pre>