Increase breaks in discrete legend

user_15529804 0
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I'm currently getting started learning R and I'm focusing on data visualisation.

For this plot, I'm displaying the count of overlapping dots on the map using geom_count which gives me the following graph

geom_count graph with only 2 legend elements

As you can see the legend only contains two elements, namely the size of the dot when 5 data points are overlapping, and the size of it when 10 data points are overlapping. How can I increase the breaks that the legend includes? I have been trying with to use discrete_x_scale in order to increase the number of breaks but I just get lost and can't manage it.

The code for my current graph is simply this

ggplot(data = mpg, mapping = aes(x = cty, y = hwy)) + 
  geom_count()

I would also like to know how to change the filling color of the dot according to the number of overlapping data points.

ggplot2 r
2 Answers

You need to modify scale_size, not scale_x:

ggplot(data = mpg, mapping = aes(x = cty, y = hwy)) +
    geom_count() +
    scale_size(breaks = c(2, 4, 6, 8))

To also change the fill colour, you can use a computed aesthetic:

ggplot(data = mpg, mapping = aes(x = cty, y = hwy, color = after_stat(n))) +
    geom_count() +
    scale_size(breaks = seq(0, 15, 3)) +
    scale_color_continuous(breaks = seq(0, 15, 3)) +
    guides(size = guide_legend(), color = guide_legend())

Note the guides call: without that, you’d get two separate legends for the size and colour below each other, rather than one merged legend.

user_19680

To address the question of changing the fill colour as well as size try by creating an explicit count variable which is used to control size and colour:

library(dplyr)
library(ggplot2)

mpg1 <- 
  mpg %>% 
  group_by(cty, hwy) %>% 
  summarise(count = n())

 
ggplot(data = mpg1, mapping = aes(x = cty, y = hwy, colour = count, size = count))+
  geom_point() +
  scale_size_continuous(breaks = seq(2, 14, by = 2))+
  scale_colour_continuous(breaks = seq(2, 14, by = 2))+
  guides(colour = guide_legend(), size = guide_legend())

Note to ensure that only one legend title appears both the breaks for size and colour need to be identical.

Created on 2021-04-01 by the reprex package (v1.0.0)

user_69365450
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