title: Adding grouped geom_vline to multiple facets
body: <p>I am trying to add vertical lines that should be specific to each plot facet. I am attempting to do this by grouping the geom_vline data by the same process as the plot data are grouped. The vertical data are from a different dataframe than the points are. The lines of code below are what I have.</p>
  
  <pre><code>plots &lt;-
    dd %&gt;%
     ggplot(aes(Date, TDS)) +
      theme_bw() +
      geom_point(aes(group = Well, color = Well), size = 1) +
      ggtitle(paste("WMA A-AX TDS")) +
      ylab("mg/L") +
      geom_smooth(aes(group= Well), method = "loess", color = "black",  se = FALSE) +
      geom_vline(data = cpdates, aes(group = Well_LOC, xintercept=as.numeric(CPT_DATE)), color ="blue", lwd=0.5, lty=1) +
      facet_grid(Well~.)
  </code></pre>
  
  <p>This code however does not group the geom_vline data but puts all of the lines in all of the facets. The grouping works for the points and the LOESS lines so why not the vlines? </p>
  
  <p><a href="https://i.stack.imgur.com/nnCIP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nnCIP.png" alt="Example plot with excess vertical lines in facets"></a></p>
  
  <p>I have tried numerous things to solve this but nothing works. Any and all suggestions would be greatly appreciated.</p>