How to reverse legend key order in ggplot2

In this tutorial, we will learn how to reverse the order of legend keys in ggplot2.

In ggplot2, when we color by a variable using color or fill argument in side aes(), we get a legend with keys showing which keys match which colors. Here we will show how to reverse the order of legend keys using guides() argument for two types of plots, one scatter plot with legend made by “color” argument, and a bar plot with colors added “fill” argument.

Let us get started by loading tidyverse.

library(tidyverse)
theme_set(theme_bw(16))

We will be using diamonds data available from tidyverse.

diamonds %>% head()

## # A tibble: 6 × 10
##   carat cut       color clarity depth table price     x     y     z
##   <dbl> <ord>     <ord> <ord>   <dbl> <dbl> <int> <dbl> <dbl> <dbl>
## 1  0.23 Ideal     E     SI2      61.5    55   326  3.95  3.98  2.43
## 2  0.21 Premium   E     SI1      59.8    61   326  3.89  3.84  2.31
## 3  0.23 Good      E     VS1      56.9    65   327  4.05  4.07  2.31
## 4  0.29 Premium   I     VS2      62.4    58   334  4.2   4.23  2.63
## 5  0.31 Good      J     SI2      63.3    58   335  4.34  4.35  2.75
## 6  0.24 Very Good J     VVS2     62.8    57   336  3.94  3.96  2.48

Reverse Legend Key orders with guides(): Example 1 – scatter plot with colored dots

Let us make a scatter plot between two variables and color by a third (categorical) variable using color argument within aes().

Here we use randomly sampled 200 data points from diamonds data to make the scatter plot using slice_sample() function.

diamonds %>% 
  slice_sample(200) %>%
  ggplot(aes(x=carat, y=price, color=cut))+
  geom_point()
ggsave("how_to_reverse_legend_key_order_legend_with_color.png")

And this is how the scatter plot looks like with default legend key ordering.

We can reverse the legend key order using guides() function with color argument. We use color argument to reverse as we created the legend earlier using color argument in aes() function. guide_legend() function with reverse = TRUE actually reverses the kegend key order.

diamonds %>% 
  slice_sample(n=200) %>%
  ggplot(aes(x=carat, y=price, color=cut))+
  geom_point()+
  guides(color = guide_legend(reverse = TRUE))
ggsave("reverse_legend_key_order_legend_with_color.png")

Reverse Legend Key orders with guides(): Example 2 with bar plot with fill color

In the second example, let us make a barplot filled with colors specified by a second variable. Heere wee use fill argument within aes() to add colors, fill the bars with colors.

diamonds %>% 
  ggplot(aes(cut, fill=clarity))+
  geom_bar()+
  scale_fill_brewer(palette="Dark2")
ggsave("how_to_reverse_legend_key_order_legend_with_fill.png")

The barplot below shows the default legend key ordering.

We can use guides() function, but this time using fill argument to reverse the legend key order here as the legend was created using fill argument within aes().

diamonds %>% 
  ggplot(aes(cut, fill=clarity))+
  geom_bar()+
  scale_fill_brewer(palette="Dark2")+
  guides(fill = guide_legend(reverse = TRUE))
ggsave("reverse_legend_key_order_for_legend_with_fill.png")