title: Ggplot2 treating missing data for daily and hourly results as geom_line
body: <p>I am plotting a graph with both hourly and daily data. I want both lines to be a geom_line, but because there are NAs in the dataframe because of the hourly and daily nature of the data. The line for the daily data is not produced and I can only get it to plot with geom_point, which I don't want.</p>
  <p>This is my code:</p>
  <pre><code>scaleFUN &lt;- function(x) sprintf(&quot;%.2f&quot;, x)
  plotlist_mAODdate &lt;- list()
  
  j = 1   # counter for plot title and index
  for (datTime in mAODdata){
    plotName &lt;- names(mAODdata)[j]
    j = j+1
    plot &lt;- 
      datTime %&gt;%
      ggplot(aes(x=DateTime)) +
      geom_point(aes(y=Rel_mAOD), col='grey') +
      geom_smooth(aes(y=Rel_mAOD), col='black') +
      geom_point(aes(y=(prcp_amt/150)+72), col='blue') +
      theme_classic() +
      labs(y='Water Depth (mAOD)', x=NULL) +
      ggtitle(plotTitles[[plotName]][1]) + 
      scale_x_datetime(
        breaks=seq(min(datTime$DateTime), max(datTime$DateTime), 
                   by= &quot;6 months&quot;), date_labels=&quot;%b-%y&quot;) +
      scale_y_continuous(labels=scaleFUN, sec.axis = sec_axis(~((.-72)*150), name='Precipitation (mm)')) +
      geom_vline(xintercept=as.POSIXct('2020-11-03 01:00:00'), col='red') +
      geom_vline(xintercept=as.POSIXct('2021-11-01 01:00:00'), col='red', linetype='dashed') +
      theme(text=element_text(size=20, family='Calibri Light')) +
      theme(plot.margin = unit(c(1, 1, 1, 1), 'cm')) +
      theme(axis.title.y=element_text(margin=margin(t=0, r=20, b=0, l=0))) +
      theme(axis.title.x=element_text(margin=margin(t=20, r=0, b=0, l=0)))
    
    plotlist_mAODdate[[plotName]] &lt;- plot
  }
  </code></pre>
  <p>This is the line that I want to use geom_line() for:</p>
  <pre><code>geom_point(aes(y=(prcp_amt/150)+72), col='blue')
  </code></pre>
  <p>This is what it currently looks like, but I'd like the blue dots to be a line:</p>
  <p><a href="https://i.stack.imgur.com/cYGXP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cYGXP.png" alt="enter image description here" /></a></p>
  <p>This is what the head of the data looks like. There are several locations hence the for loop:</p>
  <pre><code>               DateTime Rel_mAOD prcp_amt
  1   2020-03-05 17:00:00  74.0054       NA
  2   2020-03-05 18:00:00  74.0064       NA
  3   2020-03-05 19:00:00  74.0048       NA
  4   2020-03-05 20:00:00  74.0054       NA
  5   2020-03-05 21:00:00  74.0055       NA
  6   2020-03-05 22:00:00  74.0045       NA
  7   2020-03-05 23:00:00  74.0049       NA
  8   2020-03-06 00:00:00  74.0057      0.0
  9   2020-03-06 01:00:00  74.0059       NA
  10  2020-03-06 02:00:00  74.0053       NA
  11  2020-03-06 03:00:00  74.0057       NA
  12  2020-03-06 04:00:00  74.0049       NA
  13  2020-03-06 05:00:00  74.0038       NA
  14  2020-03-06 06:00:00  74.0044       NA
  15  2020-03-06 07:00:00  74.0056       NA
  16  2020-03-06 08:00:00  74.0039       NA
  17  2020-03-06 09:00:00  74.0025       NA
  18  2020-03-06 10:00:00  74.0023       NA
  19  2020-03-06 11:00:00  74.0019       NA
  20  2020-03-06 12:00:00  74.0041       NA
  21  2020-03-06 13:00:00  74.0046       NA
  22  2020-03-06 14:00:00  74.0040       NA
  23  2020-03-06 15:00:00  74.0045       NA
  24  2020-03-06 16:00:00  74.0019       NA
  25  2020-03-06 17:00:00  74.0007       NA
  26  2020-03-06 18:00:00  74.0009       NA
  27  2020-03-06 19:00:00  74.0004       NA
  28  2020-03-06 20:00:00  74.0008       NA
  29  2020-03-06 21:00:00  74.0009       NA
  30  2020-03-06 22:00:00  74.0019       NA
  31  2020-03-06 23:00:00  73.9998       NA
  32  2020-03-07 00:00:00  74.0004      0.0
  </code></pre>