title: Difference between deltat and frequency in R ts() function
body: <p>This is something that has been bugging me for a while. I've been working with (monthly) ts() objects a bit recently, and I cannot for the life of me figure out the difference between <em>frequency</em> and <em>deltat</em> in the <a href="https://stat.ethz.ch/R-manual/R-devel/library/stats/html/ts.html" rel="nofollow">R Documentation</a>:</p>
  
  <blockquote>
    <p><strong>frequency:</strong> the number of observations per unit of time.<br>
    <strong>deltat:</strong> the fraction of the sampling period between successive observations; e.g., 1/12 for monthly data. Only one of frequency or deltat should be provided.</p>
  </blockquote>
  
  <p>In my case, I have tried setting <em>frequency=12</em> and <em>deltat=(1/12)</em> in separate cases with the same data, and I cannot tell any difference in the resulting time series objects.</p>
  
  <p>From the way the descriptions are worded, I get the feeling that there has got to be a difference in their uses, I just can't put my finger on it.</p>
  
  <p>Examples of cases where only one would work and not the other would be great. <br></p>