Add a labelling function to just first or last ggplot label-CodePudding

I often find myself working with data with long-tail distributions, so that a huge amount of range in values happens in the top 1-2% of the data. When I plot the data, the upper outliers cause variation in the rest of the data to wash out, but I want to show those difference.

I know there are other ways of handling this, but I found that capping the values towards the end of the distribution and then applying a continuous color palette (i.e., in ggplot) is one way that works for me to represent the data. However, I want to ensure the legend stays accurate, by adding a >= sign to the last legend label

The picture below shows the of legend I'd like to achieve programmatically, with the >= sign drawn in messily in red.

I also know I can manually set breaks and labels, but I'd really like to just do something like, if(it's the last label) ~paste0(">=",label) else label) (to show with pseudo code)

Reproducible example: (I want to alter the plot legend to prefix just the last label)

set.seed(123)
x <- rnorm(1:1e3)
y <- rnorm(1:1e3)
z <- rnorm(1e3, mean = 50, sd = 15)

d <- tibble(x = x
            ,y = y
            ,z = z)
d %>% 
  ggplot(aes(x = x
             ,y = y
             ,fill = z
             ,color = z))  
  geom_point()  
  scale_color_viridis_c()

CodePudding user response：

One option would be to pass a function to the labels argument which replaces the last element or label with your desired label like so:

library(ggplot2)

set.seed(123)
x <- rnorm(1:1e3)
y <- rnorm(1:1e3)
z <- rnorm(1e3, mean = 50, sd = 15)

d <- data.frame(
  x = x,
  y = y,
  z = z
)

ggplot(d, aes(
    x = x,
    y = y,
    fill = z,
    color = z
  ))  
  geom_point()  
  scale_fill_continuous(labels = function(x) {
    x[length(x)] <- paste0(">=", x[length(x)])
    x
  }, aesthetics = c("color", "fill"))