I am trying to highlight only certain points on a combo line + point plot in ggplot2.

Here's a bit more background. In this data set, whenever a value goes outside a certain range, it is flagged as out of spec. In the column "in\_spec", if a value has a 0, it is out of the specified range. Here's the data:

```
dat <- structure(list(Date = structure(c(1592784000, 1592784000, 1592784000, 
                                         1592784000, 1592870400, 1592870400, 1592870400, 1592870400, 1593388800, 
                                         1593388800, 1593388800, 1593388800, 1593475200, 1593475200, 1593475200, 
                                         1593475200, 1593561600, 1593561600, 1593561600, 1593561600, 1592956800, 
                                         1593043200, 1593129600, 1593648000, 1594166400, 1594684800, 1594771200, 
                                         1594857600, 1594944000, 1594252800, 1594339200), tzone = "UTC", class = 
                                         c("POSIXct", "POSIXt")),
                      variable = c("var1", "var1", "var1", "var1", "var1", "var1", "var1", 
                                   "var1", "var1", "var1", "var1", "var1", "var1", "var1", 
                                   "var1", "var1", "var1", "var1", "var1", "var1", "var1", 
                                   "var1", "var1", "var1", "var1", "var1", "var1", "var1", 
                                   "var1", "var1", "var1"),
                      reading = c(100.1, 100.1, 100.1, 100.1, 100.09, 100.09, 100.09, 100.09, 100.14, 
                                  100.14, 100.14, 100.14, 100.13, 100.13, 100.13, 100.13, 100.14, 
                                  100.14, 100.14, 100.14, 100.08, 100.05, 90.53, 100.14, 100.14, 
                                  90.3, 100.15, 100.14, 100.13, NA, NA),
                      in_spec = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
                                  1, 1, 0, 1, 1, 0, 1, 1, 1, NA, NA)), 
                 row.names = c(NA, -31L), class = c("tbl_df", "tbl", "data.frame"))

```

Plotting the trend is easy enough and with gghighlight, I've been able to highlight the values I'm after. Here's the code and output:

```
p <- ggplot(dat, aes(x = Date, y = reading)) +
       #date along the x axis, reading as the y
    geom_point() +
       #first plot the points
    gghighlight::gghighlight(in_spec == 0) +
       #highlight points that are flagged with 0
    geom_line()
       #add the line connecting the points
p

```

[![Plot with Highlighted Points](https://i.stack.imgur.com/GmkWs.png)](https://i.stack.imgur.com/GmkWs.png)

This is almost right, except that it's connecting the two points that are "out of spec", even though they aren't actually next to each other in time.

**How can I highlight just the "out of spec" points, but leave the line connecting all the other points? The end goal would be the same plot, but with just the two highlighted points below, no line between them.**

I've tried rearranging the order of the geom\_line and geom\_point calls and having the gghighlight call in different spots too.