title: Error when plotting dates and ozone data
body: <p>I am trying to add dates to a time series plot. I would like to get the date into a format where it is read and plotted as the date. However, I am getting the error: Error</p>
  <blockquote>
  <p>in 60 * offset : non-numeric argument to binary operator.</p>
  </blockquote>
  <p>I am not sure what to try next to solve this error with my dates to get it to plot.</p>
  <p>The type is list for variable D and double for variable extractdate.</p>
  <p>I have included sample data below. I am only looking at the date and O3 columns for this plot. In R, the date data was read in as %Y-%m-%d %H.</p>
  <p>Here is the portion of my code that is giving the issue:</p>
  <pre><code>extractdate &lt;- c(CurrentOzoneVC$date)
    D &lt;- as.data.frame((c(CurrentOzoneVC$date)), format = &quot;%Y-%m-%d %H&quot;)
    dates = as.chron(D[,1], &quot;%Y-%m-%d %H&quot;)
  </code></pre>
  <p>here is some sample data:</p>
  <blockquote>
  <p>ABBR   DATE    O3  SWS VWS</p>
  <p>HAVO-VC    10/01/1986 00   -999    -999    -999</p>
  <p>HAVO-VC    10/01/1986 01   -999    -999    -999</p>
  <p>HAVO-VC    10/01/1986 02   -999    -999    -999</p>
  </blockquote>
  <p>Here is how it is read in R but with 351 dates:</p>
  <p>1986-09-30 20:00:00</p>