Key gglot2 R functions

Key ggplot2 theme options to modify the plot panel and background:

theme(
  
  plot.background = element_rect(),    # Background of the entire plot
  
  panel.background = element_rect(),   # Background of plotting area
  panel.border = element_rect(),       # Border around plotting area.
                                       # fill argument should be NA
  
  panel.grid = element_line(),         # All grid lines
  panel.grid.major = element_line(),   # Major grid lines
  panel.grid.minor = element_line(),   # Minor grid lines
  
  panel.grid.major.x = element_line(), # Vertical major grid lines
  panel.grid.major.y = element_line(), # Horizontal major grid lines
  panel.grid.minor.x = element_line(), # Vertical minor grid lines
  panel.grid.minor.y = element_line()  # Vertical major grid lines
)

Arguments of the helper functons:

• element_line(color, size, linetype). Modify grid lines color size and type.
• element_rect(fill, color, size, linetype). Modfify a rectangle element background fill, as well as, the border color, size and linetype.

To remove a particular panel grid, use element_blank() for the corresponding theme argument. For example to remove the major grid lines for the x axis, use this: p + theme(panel.grid.major.x = element_blank()).

Create a basic ggplot

library(ggplot2)
p <- ggplot(ToothGrowth, aes(factor(dose), len)) +
  geom_boxplot()
p

Change background color and grid lines

1. Change the panel background color
2. Change the plot background color

# 1. Change plot panel background color to lightblue
# and the color of major/grid lines to white
p + theme(
  panel.background = element_rect(fill = "#BFD5E3", colour = "#6D9EC1",
                                size = 2, linetype = "solid"),
  panel.grid.major = element_line(size = 0.5, linetype = 'solid',
                                colour = "white"), 
  panel.grid.minor = element_line(size = 0.25, linetype = 'solid',
                                colour = "white")
  )

# 2. Change the plot background color (not the panel)
p + theme(plot.background = element_rect(fill = "#BFD5E3"))

Remove panel border and background grid lines

R function to hide plot panel borders and gridlines: element_blank().

p + theme(
  # Hide panel borders and remove grid lines
  panel.border = element_blank(),
  panel.grid.major = element_blank(),
  panel.grid.minor = element_blank(),
  # Change axis line
  axis.line = element_line(colour = "black")
  )

Remove grey background color

• Solution 1: Use the theme functions to get rid of the grey background (@ref(ggplot-themes-gallery).

p + theme_bw()  # Black and white theme

p + theme_classic() # Classic theme

• Solution 2: Create, step-by-step, a ggplot with white background:

p + theme(
  # Remove panel border
  panel.border = element_blank(),  
  # Remove panel grid lines
  panel.grid.major = element_blank(),
  panel.grid.minor = element_blank(),
  # Remove panel background
  panel.background = element_blank(),
  # Add axis line
  axis.line = element_line(colour = "grey")
  )

Make a ggplot with transparent background

In this section you will learn how to make and save a ggplot with transparent background.

• Solution 1: Use the function theme_transparent() [in ggpubr package]. First, install it with install.packages("ggpubr"), then type this:

transparent.plot <- p + ggpubr::theme_transparent()
ggsave(filename = "transparent-background.png",
       plot = transparent.plot,
       bg = "transparent", 
       width = 2, height = 1.5, units = "in")

• Solution 2: Make a transparent background by starting from theme_void():

p + theme_void() + # Empty theme without axis lines and texts
  theme(
    panel.background = element_rect(fill = "transparent", colour = NA),
    plot.background = element_rect(fill = "transparent", colour = NA),
    legend.background = element_rect(fill = "transparent", colour = NA),
    legend.box.background = element_rect(fill = "transparent", colour = NA)
  )

Create a ggplot with black background

Start by creating a simple scatter plot:

sp <- ggplot(iris, aes(Sepal.Length, Sepal.Width))+
  geom_point(aes(color = Species, shape = Species))+
  stat_smooth(aes(color = Species, fill = Species), 
              method = "lm", alpha = 0.2)+
  scale_color_manual(values = c("#E4F00A", "white", "#22FF00")) + 
  scale_fill_manual(values = c("#E4F00A", "white", "#22FF00")) 

Use the dark theme function – theme_dark():

sp + theme_dark() 

Create a ggplot with a black background:

sp + theme(
  # get rid of panel grids
  panel.grid.major = element_blank(),
  panel.grid.minor = element_blank(),
  # Change plot and panel background
  plot.background=element_rect(fill = "gray"),
  panel.background = element_rect(fill = 'black'),
  # Change legend 
  legend.position = c(0.6, 0.07),
  legend.direction = "horizontal",
  legend.background = element_rect(fill = "black", color = NA),
  legend.key = element_rect(color = "gray", fill = "black"),
  legend.title = element_text(color = "white"),
  legend.text = element_text(color = "white")
  )

Conclusion

This article shows how to change a ggplot theme background color and grid lines. The essentials are summarized below:

• Create an example of ggplot:

library(ggplot2)
p <- ggplot(ToothGrowth, aes(factor(dose), len)) +
  geom_boxplot()
p

• Change ggplot background color:
  • use the standard ggplot2 themes (theme_classic(), theme_bw(), theme_minmal(), theme_light(), etc)
  • or, edit the theme function as follow.

# Create a ggplot with white background
p + theme(
  plot.background = element_rect(fill = "white"),
  panel.background = element_rect(fill = "white"),
  axis.line.x = element_line(color = "grey")
  )

• Create a ggplot with transparent background. The easiest solution is to use the theme_transparent() function [in ggpubr]

p + ggpubr::theme_transparent()