如何在barplot中更改ggplot2 x轴值？

Question

I would like to make a barplot in R, where the last bar in the graph indicates that last is the sum of all values whose the frequency is greater than a certain threshold. I want to represent this information on x-value correspondent to the last bar. For instance:

library(ggplot2)

x <- c(1, 2, 3, 4, 5)
y <- c(4000, 3000, 2000, 1000, 500)

df <- data.frame(x, y)

names(df) <- c("Var1", "Freq")

theme_set(theme_classic())

g <- ggplot(df, aes(Var1, Freq))
g + geom_bar(stat = "identity", width = 0.5, fill = 'tomato2') + 
  xlab('Var1') +
  ylab('Freq') +
  theme(axis.text.x = element_text(angle = 0, 
                                   vjust = 0.6, 
                                   colour = "black"),
        axis.text.y = element_text(colour = "black"))

The above code produces a chart similar to this:

But on the last bar, I want that last value of x-axis ( x = 5 ) be displayed as >= 5 .

So far, I've tried to use scale_x_discrete . So I added to the above code the following lines:

n <- 5

# I'm not very creative with names.
.foo <- function(x, n) {
  if (x == n) {
    element <- paste('\u2265', toString(x), sep = ' ')
  } else {
    element <- toString(x)
  }
}

labels <- sapply(seq(n), .foo, n)

g + scale_x_discrete(breaks = sapply(seq(n), function(x) toString(x)),
                     labels = labels)

This code formats the x-axis as I wish but it overrides the barplot, leaving an empty chart:

How can I do this?

Answer 1

Change the labels in scale_x_continuous :

... + scale_x_continuous(labels=c("0", "1", "2", "3", "4", "\u2265 5"))

Answer 2

One approach would be to avoid changing the axis tick labels directly, but convert your categorical data in Var1 to a factor, then relevel that factor using forcats::fct_lump such that the final factor is ≥5

# Insert after df generated, before plot call
library(forcats)
df <- df %>% 
  mutate(Var1 = as_factor(Var1),
         Var1 = fct_lump_min(Var1, min = 501, w = Freq, other_level = "≥5"))

Answer 3

The problem was that, as pointed out by @Z.Lin comment, I was assign the geom_bar(...) to the ggplot object before using scale_x_discret . Here is the solution:

library(ggplot2)
  ...
  labels <- sapply(seq(n), .foo, n)

  g <- ggplot(df, aes(Var1, Freq)) + 
         scale_x_discrete(breaks = sapply(seq(n), function(x) toString(x)),
                          labels = labels)

  g + geom_bar(stat = "identity", width = 0.5, fill = color) + 
  ...