I have a ggplot of temperature values plotted against time. I’d like to add vertical lines to my graph where temperature exceeds a threshold (let’s say 12 degrees).
reprex:
#example data
Temp <- c(10.55, 11.02, 6.75, 12.55, 15.5)
Date <- c("01/01/2000", "02/01/2000", "03/01/2000", "04/01/2000", "05/01/2000")
#data.frame
df1 <- data.frame(Temp, Date)
#plot
df1%>%
ggplot(aes(Date, format(as.numeric(Temp))))+
geom_line(group=1)
I thought I could maybe do something with geom_hline and then rotate 90 degrees. I went about this by trying to create an object of all values (to 2dp) between 12 and 20. I would then tell geom_hline to use that object to match values and draw the lines.
Then I get a bit stuck. I don’t really know how to rotate the lines or whether that’s even a good idea.
Disclaimer: I know my dates are not actually dates in the reprex, but they are in my rle.
>Solution :
geom_vline can accept an xintercept either
-
in the
xinterceptparameter (if you want to specify it manually) or -
in
aes(xintercept = ...)if you want to use values from a data frame. We can usedata = . %>% filter...to use the same data frame that came into ggplot, but apply some further manipulations.
df1 %>%
mutate(Date = as.Date(Date, "%m/%d/%Y")) %>%
ggplot(aes(Date, Temp)) +
geom_line() +
geom_vline(data = . %>% filter(Temp > 12),
aes(xintercept = Date))
