Basic ggplot

Data: ToothGrowth

# Convert the column dose to factor variable
data("ToothGrowth")
ToothGrowth$dose <- as.factor(ToothGrowth$dose)

# Create a simple boxplot
library(ggplot2)
p <- ggplot(ToothGrowth, aes(x = dose, y = len)) + 
  geom_boxplot()

Change themes

p + theme_gray(base_size = 14) 

p + theme_bw()

p + theme_linedraw()

p + theme_light()

p + theme_dark() 

p + theme_minimal()

p + theme_classic()

p + theme_void()

install.packages("ggthemes") # Install 

library(ggthemes) # Load

# Scatter plot
sp <- ggplot(mtcars, aes(wt, mpg)) +
  geom_point() 
sp

# Boxblot
ToothGrowth$dose <- as.factor(ToothGrowth$dose)
bxp <- ggplot(ToothGrowth, aes(x = dose, y = len)) +
  geom_boxplot(aes(fill = dose))
bxp

library(ggthemes)
sp + geom_rangeframe() +  theme_tufte()

p <- ggplot(ToothGrowth, aes(factor(dose), len)) +
  theme_tufte(ticks = FALSE)

# Box plot 1
p + geom_tufteboxplot()

# Box plot 2
p + geom_tufteboxplot(median.type = "line", 
                      whisker.type = 'line',
                      hoffset = 0, width = 3)

bxp + theme_economist() + scale_fill_economist()

bxp + theme_stata() + scale_fill_stata()

bxp + theme_hc()+ scale_colour_hc()

Override the current theme: theme_set

The function theme_set() can be used to change the theme for the entire session. It returns the old theme, so that we can restore it later.

p <- ggplot(ToothGrowth, aes(x = dose, y = len)) + 
  geom_boxplot()
# Set theme_bw()
old.theme <- theme_set(theme_bw())
p

# Restore the old theme
theme_set(old.theme)
p

Change ggplot theme base_size and base_family

Note that, the theme functions can take the two arguments below :

• base_size: base font size (to change the size of all plot text elements)
• base_family: base font family

For example, the size of all the plot text elements can be easily changed at once, using:

p + theme_gray(base_size = 18, base_family = "Times")

Create a custom theme

The function theme() is used to control non-data parts of a ggplot2 graph, including

• Line elements: axis lines, minor and major grid lines, plot panel border, axis ticks background color, etc.
• Text elements: plot title, axis titles, legend title and text, axis tick mark labels, etc.
• Rectangle elements: plot background, panel background, legend background, etc.

There is a specific function to modify each of these three elements :

• element_line(color, size, linetype) to modify the line elements of the theme
• element_text(face, color, size, hjust, vjust, angle) to modify the text elements
• element_rect(fill, color, size, linetype) to modify the rectangle elements

The easiest way to create a custom theme is, for example, to extract and modify the R code of the function theme_gray() or any other theme functions [theme_bw(), theme_classic(), etc].

• Build your theme from scrach by starting with the source code of the function theme_gray():

theme_gray

function (base_size = 11, base_family = "") {
  
 half_line <- base_size/2
 
theme(
  ...
  axis.text = element_text(size = rel(0.8), colour = "grey30"),
  ...
  )

}

• Create a new theme called theme_bluewhite() by starting with the source code of the function theme_bw(). We’ll replace only some theme elements.

# Create a new theme
theme_bluewhite <- function (base_size = 11, base_family = "") {
    theme_bw() %+replace% 
    theme(
      panel.grid.major  = element_line(color = "white"),
      panel.background = element_rect(fill = "lightblue"),
      panel.border = element_rect(color = "lightblue", fill = NA),
      axis.line = element_line(color = "lightblue"),
      axis.ticks = element_line(color = "lightblue"),
      axis.text = element_text(color = "steelblue")
      )
}

# Using our new theme
ggplot(ToothGrowth, aes(dose, len)) +
  geom_boxplot() +
  theme_bluewhite()

Conclusion

We present a list of ggplot themes to easily customize your graphs. We also describe how to create a custom ggplot theme.

The main points as shown below.

• Create an example of ggplot:

library(ggplot2)
p <- ggplot(ToothGrowth, aes(x = dose, y = len)) + 
  geom_boxplot()

• Change ggplot the background theme by using one of the following professional themes:
  • theme_bw(), theme_minimal(), theme_classic() and theme_dark() [in ggplot2 package]
  • theme_tufte() and theme_economist() [in ggthemes]

p + theme_minimal()