A Complete Guide on the Viridis Color Palettes

scale_color_viridis_*() with suffix d, c, or b

The basic formula of a viridis color scale is scale_color_viridis_*(), with * referring to three suffix options, including d, c, and b, depending on the type of the variable that is mapped to the color aesthetic. The palette is selected using argument e.g. option = "C" or option = "plasma" (see names and associated alphabets above).

• When a categorical variable is mapped to color, use scale_color_viridis_d to create discrete color legends.

# packages and global themelibrary(ggplot2)library(dplyr)theme_set(theme_bw(base_size = 14))
base <- iris %>% ggplot(aes(Sepal.Length, Sepal.Width)) 
base +   geom_jitter(aes(color = Species), size = 3) + # Species a categorical variable  scale_color_viridis_d(option = "D") # use suffix 'd' for discrete color scale

When a numerical variable is mapped to color:

• use scale_color_viridis_c to generate continuous color bar, or
• use scale_color_viridis_b to create binned (stepwise) color scale.

base +   # Petal.Length a numeric variable  geom_jitter(aes(color = Petal.Length), size = 3) +   # use suffix 'c' for continuous color scale  scale_color_viridis_c(option = "D") 

base +   geom_jitter(aes(color = Petal.Length), size = 3) +   # use suffix "b" for binned color legend  scale_color_viridis_b(option = "D") 

In like manner, scale_fill_viridis_*() is used for the fill aesthetic, with the suffix options following the same rules above.

Extract colors from viridis palettes

The above scale_color_viridis_*() functions are built-in ggplot2, and are directly available once the package ggplot2 is loaded. However, in order to extract color hex codes from the viridis palettes, you need to additionally load the viridis package.

library(viridis)# extract 20 colors from palette option Aa <- viridis(20, option = "A")a

Output:
 [1] "#000004FF" "#07071DFF" "#160F3BFF" "#29115AFF" "#400F73FF" "#56147DFF"
 [7] "#6B1D81FF" "#802582FF" "#952C80FF" "#AB337CFF" "#C03A76FF" "#D6456CFF"
[13] "#E85362FF" "#F4685CFF" "#FA815FFF" "#FD9A6AFF" "#FEB37BFF" "#FECC8FFF"
[19] "#FDE4A6FF" "#FCFDBFFF"

Unlike the brewer palettes which are subjected to the maximum color number limits, the viridis palette has no such limit; it allows an unlimited number of transitional colors to be automatically interpolated and extracted.

Use the scales package to visualize the color hex codes.

library(scales)show_col(a, cex_label = .6) # use 'cex_label' to set label size

Display colors from the viridis palettes

There is no simple function to display the color scales in an easy way. However, you can plot out the palettes using the following script. The script is contributed by Prof. José María Sallan Leyes at Universitat Politècnica de Catalunya.

viridis_names <-c(  "A (magma)", "B (inferno)", "C (plasma)", "D (viridis)",   "E (cividis)", "F (rocket)", "G (mako)", "H (turbo)")
n <- 50 # control the smoothness of color transitionpar(mfrow=c(4,2), mar = rep(1, 4))
f <- sapply(1:8, function(x) image(  matrix(1:n, n, 1),   col = viridis(n = n, option = LETTERS[x]),   axes =FALSE, main = viridis_names[x], cex.main = 1.5))