title: Mark a period of time in a time-series-plot
body: <p>First, let's create some fake data:</p>
  
  <pre><code>d &lt;- c("2019-01-01", "2019-01-02", "2019-01-03", "2019-01-04", "2019-01-03", "2019-04-06", "2019-04-03", "2019-05-07", "2019-05-03", "2019-05-03", "2019-05-03", "2019-05-03", "2019-06-03", "2019-06-03", "2019-06-03", "2019-06-03", "2019-06-03", "2019-06-03", "2019-06-03", "2019-07-03", "2019-07-03", "2019-07-04", "2019-08-03", "2019-09-05", "2019-09-03", "2019-09-03", "2019-09-06", "2019-09-08", "2019-10-03", "2019-11-03", "2019-11-03", "2019-11-03", "2019-11-03", "2019-11-03", "2019-11-03", "2019-12-03", "2019-12-03")
  
  df &lt;- data.frame(dates=as.Date(d))
  </code></pre>
  
  <p>Now, I create a time-series plot:</p>
  
  <pre><code># aggregate data
  df_plot &lt;- df %&gt;% mutate(month = lubridate::floor_date(dates, "month")) %&gt;% 
    group_by(month) %&gt;% summarise(count = n())
  
  # plot data
  ggplot(aes(x = month, y = count), data = df_plot) + geom_line() +
    scale_x_date() +
    geom_vline(xintercept = as.numeric(as.Date("2019-01-30")), linetype=4)
  
  </code></pre>
  
  <p>With <code>geom_vline(xintercept = as.numeric(as.Date("2019-01-30")), linetype=4)</code> I can mark a certain date with a vertical line. Is there also a possibility to mark a time-<em>range</em> (let's say from 2019-01-30 to 2019-02-15) with a colored box or something?</p>