Add total number to ggplot legend

June 9, 2022

I made a frequency barplot with the following data and code:

structure(list(Geslacht = c("man", "man", "man", "man", "man", 
"man", "man", "vrouw", "vrouw", "vrouw", "vrouw", "vrouw", "vrouw", 
"vrouw", "vrouw"), Lengteklasse = c(6, 7, 8, 9, 10, 11, 12, 6, 
7, 8, 9, 10, 11, 12, 13), Freq = c(1L, 9L, 19L, 21L, 35L, 22L, 
5L, 2L, 13L, 19L, 37L, 45L, 40L, 6L, 1L)), class = c("grouped_df", 
"tbl_df", "tbl", "data.frame"), row.names = c(NA, -15L), groups = structure(list(
    Geslacht = c("man", "vrouw"), .rows = structure(list(1:7, 
        8:15), ptype = integer(0), class = c("vctrs_list_of", 
    "vctrs_vctr", "list"))), class = c("tbl_df", "tbl", "data.frame"
), row.names = c(NA, -2L), .drop = TRUE))

ggplot(Freq_lengteklasse, aes(Lengteklasse, Freq, fill = Geslacht))+
  geom_col()+
  scale_x_continuous(breaks = seq(6,13, by = 1))+
  scale_y_continuous(breaks = seq(0,80, by = 10))+
  labs(x = "Lengteklasse (cm)", y = "Frequentie")+
  scale_fill_manual(values=c('lightgray','black'))+
  theme_classic()

I want to add the total count of man and vrouw which should say n = 275, positioned under the legend. How would one do this?

>Solution :

You can add a tag in your labs which will display the total number. You can change the position of the tag in the theme with plot.tag.position. You can use the following code:

library(tidyverse)
ggplot(Freq_lengteklasse, aes(Lengteklasse, Freq, fill = Geslacht))+
  geom_col()+
  scale_x_continuous(breaks = seq(6,13, by = 1))+
  scale_y_continuous(breaks = seq(0,80, by = 10))+
  labs(x = "Lengteklasse (cm)", y = "Frequentie", tag = paste('n =', sum(Freq_lengteklasse$Freq)))+
  scale_fill_manual(values=c('lightgray','black'))+
  theme_classic() +
  theme(plot.tag.position = c(0.95, 0.4))

Output: