How to use directlabels to label lines in ggplot2

Question

library(ggplot2)
library(directlabels)
mydat <- structure(list(Name = c("Ana", "Josh", "Bart", "Ana", "Josh", 
"Bart"), color_line = c("purple", "purple", "orange", "purple", 
"purple", "orange"), x = c(0.864864864864865, 0.810810810810811, 
0.472972972972973, 0.851351351351351, 0.702702702702703, 0.648648648648649
), y = c(0.702702702702703, 0.675675675675676, 0.797297297297297, 
0.797297297297297, 0.72972972972973, 0.635135135135135), Class = c("A", 
"A", "A", "B", "B", "B")), class = c("data.table", "data.frame"
), row.names = c(NA, -6L))

mydat
   Name color_line         x         y Class
1:  Ana     purple 0.8648649 0.7027027     A
2: Josh     purple 0.8108108 0.6756757     A
3: Bart     orange 0.4729730 0.7972973     A
4:  Ana     purple 0.8513514 0.7972973     B
5: Josh     purple 0.7027027 0.7297297     B
6: Bart     orange 0.6486486 0.6351351     B

I have the above data set, and I plotted the results as follows:

g <- ggplot(mydat, aes(x = x, y = y, color = Class)) + 
       theme_classic() + 
       geom_line(mapping = aes(group = Name), color = mydat$color_line) + 
       geom_point() + 
       scale_color_manual(values=c("springgreen4", "royalblue3"))
g

Now, I would like to add the Name of each individual to each line. Something that might look like this:

The closest thing that I found is the angled.boxes in library(directlabels). You can see how it looks here.

However, when I tried the following, I got a different plot.

direct.label(g, "angled.boxes")

score 4 · Accepted Answer · answered Dec 12 '22 at 00:51

One option to achieve your desired result would be to use the geomtextpath package which adds lots of options to add direct labels to lines and even allows for curved text. For your use case you could simply replace geom_line by geomtextpath::geom_textline to add your labels.

Note: Additionally I slightly adjusted your code to make use of the color aes for the lines and the fill aes to color the points.

library(ggplot2)
library(geomtextpath)

pal_color <- c("purple", "purple", "orange")
names(pal_color) <- c("Ana", "Josh", "Bart")

pal_fill <- c("springgreen4", "royalblue3")
names(pal_fill) <- c("A", "B")

base <- ggplot(mydat, aes(x = x, y = y)) + 
  scale_color_manual(values = pal_color) +
  scale_fill_manual(values= pal_fill) +
  theme_classic() +
  guides(color = "none")

base +
  geomtextpath::geom_textline(
    aes(group = Name, color = Name, label = Name), textcolour = "black") +
  geom_point(aes(fill = Class), shape = 21, stroke = 0, size = 2)

Or using the offset and gap arguments you could add the labels on top of the lines:

base +
  geomtextpath::geom_textline(
    aes(group = Name, color = Name, label = Name),
    offset = unit(5, "pt"), gap = FALSE, textcolour = "black") +
  geom_point(aes(fill = Class), shape = 21, stroke = 0, size = 2)

thank you. this is perfect! Just a follow up question, how can one change the width of the lines? — Adrian, Dec 12 '22 at 03:20
You could set the line width with the `linewidth` aes or argument, i.e. `geomtextpath::geom_textline(..., linewidth = 2)`. — stefan, Dec 12 '22 at 06:29

score 0 · Answer 2 · answered Dec 12 '22 at 00:03

It's not ideal, but I did this a long time ago using some math and manual adjustments

mydat %>% 
  group_by(Name) %>% 
  mutate(
    posx = mean(x)*1.01,
    posy = mean(y)*1.01,
    angle = -60*diff(range(y))/diff(range(x))
    ) %>% 
  ggplot(aes(x = x, y = y, color = Class)) + theme_classic() +
  geom_line(mapping = aes(group = Name), color = mydat$color_line) +
  geom_point() + scale_color_manual(values=c("springgreen4", "royalblue3"))+
  geom_text(aes(x = posx, y = posy, group = Name, label = Name, angle = angle),
            size = 6, show.legend = FALSE, color = "black")

How to use directlabels to label lines in ggplot2

2 Answers2