How to pass an expression to a geom_text label in ggplot? - r

Question

I am attempting to pass an expression with subscript to a single geom_text() label in ggplot. Here is my code right now:
my_exp <- expression('my_exp'[s][u][b])
my_data <-
data.frame(
var_1 = c("a", "b", "c"),
var_2 = c(1, 2, 3)
)
my_data %>%
ggplot(aes(x = var_1, y = var_2))+
geom_text(aes(label = var_1))
Here is the resulting plot:
What I would like to do is replace the var_1 value of "a" with the expression specified by my_exp and then have geom_text() evaluate that value as an expression, resulting in the subscript appearing on the ggplot.

Answer 1

I would suggest this approach. You can build another variable for your labels and then enable the option parse=T from geom_text() in order to have the desired plot. Here the code:
library(ggplot2)
library(tidyverse)
#Data
my_exp <- as.character(expression('my_exp'[s][u][b]))
my_data <-
data.frame(
var_1 = c("a", "b", "c"),
var_2 = c(1, 2, 3),stringsAsFactors = F
)
#Mutate
my_data$label <- ifelse(my_data$var_1=='a',my_exp,my_data$var_1)
#Plot
my_data %>%
ggplot(aes(x = var_1, y = var_2))+
geom_text(aes(label = label),parse = T)
Output:
Update: If there are issues with labels here a code for that:
#Label
my_exp <- "14~M~my_exp[s][u][b]"
#Code
my_data <-
data.frame(
var_1 = c("a", "b", "c"),
var_2 = c(1, 2, 3),stringsAsFactors = F
)
#Mutate
my_data$label <- ifelse(my_data$var_1=='a',my_exp,my_data$var_1)
#Plot
my_data %>%
ggplot(aes(x = var_1, y = var_2))+
geom_text(aes(label = label),parse = T)
Output: