add significance asterisk manually in ggplot2-CodePudding

I have a time series DataFrame in R. There are 4 groups and the data of each group (variable) is acquired at 3 different timepoints.

Group Timepoint Variable 
A        1 1.4705745 
B        1 4.6090900
C        1 2.2480962
D        1 1.6443650
E        1 4.4812444
A        2 0.8026552
B        2 4.7803944
C        2 1.3743527
D        2 4.0399467
E        2 3.5651057 
A        3 4.7275369
B        3 2.4491532
C        3 3.9508347
D        3 3.4278974
E        3 0.6917490

I made a line plot using the following code,

plot_data <- ggplot(data, aes(x = Timepoint, y = Variable, color = Group, group = Group)) geom_line() 
  scale_color_discrete("Group") 
  scale_y_continuous(limits = c(0, 6))
plot_data

but also want to add significant asterisk, for instance, like that. Is there any way to add asterisk to the plot manually?

CodePudding user response：

You can use annotate like this:

library(ggplot2)
plot_data <- ggplot(data, aes(x = Timepoint, y = Variable, color = Group, group = Group)) geom_line() 
  scale_color_discrete("Group") 
  scale_y_continuous(limits = c(0, 6))  
  annotate('text', x = 1, y = c(5,5.2), label='"*"', parse=TRUE, color = c("pink", "yellow"))  
  annotate('text', x = 3, y = c(5,5.2), label='"*"', parse=TRUE, color = c("red", "green"))

plot_data

^{Created on 2022-09-02 with reprex v2.0.2}

To get the exact same colors as in standard ggplot you can check that by using hue_pal like this:

library(ggplot2)
library(scales)
show_col(hue_pal()(5))

plot_data <- ggplot(data, aes(x = Timepoint, y = Variable, color = Group, group = Group)) geom_line() 
  scale_color_discrete("Group") 
  scale_y_continuous(limits = c(0, 6))  
  annotate('text', x = 1, y = c(5,5.2), label='"*"', parse=TRUE, color = c("#A3A500", "#E76BF3"))  
  annotate('text', x = 3, y = c(5,5.2), label='"*"', parse=TRUE, color = c("#F8766D", "#00BF7D"))

plot_data

^{Created on 2022-09-02 with reprex v2.0.2}