[R] How to use ggpattern to add patterns to ggplot2 plots
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Adding patterns to plots is a great way to improve accessibility (making plots colorblind-friendly) and to add an extra dimension of information. The ggpattern package provides a rich set of tools to achieve this in ggplot2.
Basic Example with mtcars
Let’s start with a barplot using the mtcars dataset. We will map cyl to the x-axis, mpg to the y-axis, use gear for the fill color, and am for the pattern.
# Prepare data
df <- mtcars %>%
mutate(
cyl = factor(cyl),
gear = factor(gear),
am = factor(am, labels = c("Automatic", "Manual"))
)
# Create barplot
ggplot(df, aes(x = cyl, y = mpg, fill = gear)) +
geom_bar_pattern(
aes(pattern = am),
stat = "identity",
position = "dodge",
color = "black",
pattern_fill = "black",
pattern_spacing = 0.02,
pattern_key_scale_factor = 1.5
) +
scale_pattern_manual(values = c("stripe", "crosshatch")) +
labs(
title = "MPG by Cylinders, Gear, and Transmission",
subtitle = "Patterns representing transmission type",
x = "Cylinders",
y = "Miles Per Gallon (MPG)",
fill = "Gears",
pattern = "Transmission"
) +
theme_minimal()
Exploring Key Parameters
The ggpattern package allows for fine-grained control over how patterns are rendered. Here are some of the most important parameters:
1. pattern_key_scale_factor
This parameter scales the pattern density specifically in the legend. Without it, patterns in the legend can often be hard to see. Reduce the value will make it easier fit into the legend keys.
p_base <- ggplot(df, aes(x = cyl, y = mpg, fill = gear)) +
geom_bar_pattern(
aes(pattern = am),
stat = "identity",
position = "dodge",
color = "black",
pattern_spacing = 0.02
) +
theme_minimal() +
labs(title = "Default vs Scaled Legend")
# Default legend
p1 <- p_base + labs(subtitle = "Default (key_scale_factor = 1)")
# Scaled legend
p2 <- p_base +
geom_bar_pattern(
aes(pattern = am),
stat = "identity",
position = "dodge",
color = "black",
pattern_spacing = 0.02,
pattern_key_scale_factor = 0.5
) +
labs(subtitle = "Scaled (key_scale_factor = 0.5)")
p1
p2
2. pattern_spacing and pattern_density
pattern_spacing controls the distance between pattern elements (lower = denser), while pattern_density controls the coverage (higher = denser).
# Spacing effect
ggplot(df, aes(x = cyl, y = mpg, fill = gear)) +
geom_bar_pattern(
aes(pattern = am),
stat = "identity",
position = "dodge",
pattern_spacing = 0.2, # Wider spacing
pattern_key_scale_factor = 1.5
) +
labs(title = "Effect of pattern_spacing = 0.5 (Sparser)") +
theme_minimal()
# Density effect
ggplot(df, aes(x = cyl, y = mpg, fill = gear)) +
geom_bar_pattern(
aes(pattern = am),
stat = "identity",
position = "dodge",
pattern_density = 0.8, # Higher density
pattern_key_scale_factor = 1.5
) +
labs(title = "Effect of pattern_density = 0.8 (Denser)") +
theme_minimal()
3. pattern_fill
pattern_fill sets the color of the pattern elements themselves.
ggplot(df, aes(x = cyl, y = mpg, fill = gear)) +
geom_bar_pattern(
aes(pattern = am),
stat = "identity",
position = "dodge",
pattern_fill = "white", # White pattern lines
pattern_density = 0.5, # make it bigger so that the color is easier to see
pattern_spacing = 0.02,
pattern_key_scale_factor = 1.5
) +
labs(title = "Effect of pattern_fill = 'white'") +
theme_minimal()
4. pattern_shape
For geometric patterns like regular_polygon, pattern_shape controls the number of sides.
ggplot(df, aes(x = cyl, y = mpg, fill = gear)) +
geom_bar_pattern(
aes(pattern_shape=gear),
pattern = "regular_polygon",
stat = "identity",
position = "dodge",
pattern_size = 0.5, # stroke line width
pattern_density = 0.5, # increase the shape size
pattern_spacing = 0.03,
pattern_key_scale_factor = 1.5
) +
scale_pattern_shape_manual(values = c("3"="circle", "4"="convex6", "5"="square")) + # manually set shapes
labs(title = "Effect of mapping pattern_shape to gear") +
theme_minimal()
Troubleshooting
If you encounter issues installing or loading ggpattern on Linux, you may need to install the following system dependencies:
sudo apt-get install libudunits2-dev sudo apt install libproj22 sudo apt-get install libgdal-dev
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