How to Assign Colors to Categorical Variable in ggplot2 Plot in R ?

In this article, we will see how to assign colors to categorical Variables in the ggplot2 plot in R Programming language. 

Note: Here we are using a scatter plot, the same can be applied to any other graph.

Dataset in use:

	Year	Points	Users
1	2011	30	user1
2	2012	20	user2
3	2013	15	user3
4	2014	35	user4
5	2015	50	user5

To Create an R plot, we use ggplot() function and to make it scatter plot we add geom_point() function to ggplot() function. By Default, the plot has following colors.

Example:

R

# Load Library
library(ggplot2)

# Create DataFrame for Plotting.
data <- data.frame(Year = c(2011, 2012, 2013, 2014, 2015),
                   Points = c(30, 20, 15, 35, 50),
                   Users = c("user1", "user2", "user3",
                             "user4", "user5"))

# Create ggplot2 ScatterPlot.
ggplot(data, aes(Year, Points, color = Users)) +
  geom_point(size = 10)

Output:

ScatterPlot using ggplot2 with default colors

In R Programming, we have many in built function for creating our own discrete scales such as scale_fill_manual, scale_size_manual, scale_shape_manual, scale_linetype_manual, etc. To assign desired colors to categorical data, we use one of them scale_color_manual() function, which is used to scale (map) the manual colors.

Syntax : scale_color_manual(values)

Parameter :

• values : A set of aesthetic values to map the data. Here we take desired set of colors.

Return : Scale the manual values of colors on data.

Example:

R

# Load Library
library(ggplot2)

# Create DataFrame for Plotting
data <- data.frame(Year = c(2011, 2012, 2013, 2014, 2015),
                   Points = c(30, 20, 15, 35, 50),
                   Users = c("user1", "user2", "user3",
                             "user4", "user5"))

# Create a ScatterPlot with fixed colors of
# points(data).
ggplot(data, aes(Year, Points, color = Users)) +
  geom_point(size = 10)+
  scale_color_manual(values = c("green", "orange", "red",
                                "yellow", "blue"))

Output :

Plot with fixed colors