R ggplot text on grid lines denoting grid line value

melmo 0
Viewed 19

Does anyone know how to make the the value of the grid line appear on the grid line in ggplot2?

I have a very large plot that I want to display the grid line value on intermittently throughout the plot, so when you are zoomed in you can easily tell what the value is. The only way I can currently think to do that is to add the labels with another data frame or something with the label and the x, y position. I was wondering if there was a more efficient way or an actual built in mechanism to do this.

Thanks!

r
1 Answers

There is no option built-in to do this specifically, but it is pretty straightforward using expand.grid to create the grid points and labels, then simply draw the result on with geom_text:

library(ggplot2)

gridlines <- expand.grid(Petal.Width = seq(0, 2, 0.5), 
                         Sepal.Length = seq(4, 8), 
                         Species = "setosa")

ggplot(iris, aes(Sepal.Length, Petal.Width, color = Species)) +
  geom_point() +
  geom_text(data = gridlines, color = "gray50", aes(label = Sepal.Length), 
            angle = 90, vjust = -0.5, nudge_y = 0.25) +
  geom_text(data = gridlines, color = "gray50", aes(label = Petal.Width),
            vjust = -0.5, nudge_x = 0.5) +
  theme_bw(base_size = 20) +
  theme(panel.grid.minor = element_blank())

enter image description here

Created on 2022-09-05 with reprex v2.0.2

Allan Cameron0
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