Most basic barplot with `geom_bar()`

This is the most basic barplot you can build using the ggplot2 package. It follows those steps:

always start by calling the ggplot() function.
then specify the data object. It has to be a data frame. And it needs one numeric and one categorical variable.
then come thes aesthetics, set in the aes() function: set the categoric variable for the X axis, use the numeric for the Y axis
finally call geom_bar(). You have to specify stat="identity" for this kind of dataset.

# Load ggplot2
library(ggplot2)

# Create data
data <- data.frame(
  name=c("A","B","C","D","E") ,  
  value=c(3,12,5,18,45)
  )

# Barplot
ggplot(data, aes(x=name, y=value)) + 
  geom_bar(stat = "identity")

Control bar color

Here are a few different methods to control bar colors. Note that using a legend in this case is not necessary since names are already displayed on the X axis. You can remove it with theme(legend.position="none").

# Libraries
library(ggplot2)

# 1: uniform color. Color is for the border, fill is for the inside
ggplot(mtcars, aes(x=as.factor(cyl) )) +
  geom_bar(color="blue", fill=rgb(0.1,0.4,0.5,0.7) )
 
# 2: Using Hue
ggplot(mtcars, aes(x=as.factor(cyl), fill=as.factor(cyl) )) + 
  geom_bar( ) +
  scale_fill_hue(c = 40) +
  theme(legend.position="none")
 
# 3: Using RColorBrewer
ggplot(mtcars, aes(x=as.factor(cyl), fill=as.factor(cyl) )) + 
  geom_bar( ) +
  scale_fill_brewer(palette = "Set1") +
  theme(legend.position="none")

 
# 4: Using greyscale:
ggplot(mtcars, aes(x=as.factor(cyl), fill=as.factor(cyl) )) + 
  geom_bar( ) +
  scale_fill_grey(start = 0.25, end = 0.75) +
  theme(legend.position="none")

 
# 5: Set manualy
ggplot(mtcars, aes(x=as.factor(cyl), fill=as.factor(cyl) )) +  
  geom_bar( ) +
  scale_fill_manual(values = c("red", "green", "blue") ) +
  theme(legend.position="none")

Horizontal barplot with `coord_flip()`

It often makes sense to turn your barplot horizontal. Indeed, it makes the group labels much easier to read.

Fortunately, the coord_flip() function makes it a breeze.

# Load ggplot2
library(ggplot2)

# Create data
data <- data.frame(
  name=c("A","B","C","D","E") ,  
  value=c(3,12,5,18,45)
  )

# Barplot
ggplot(data, aes(x=name, y=value)) + 
  geom_bar(stat = "identity") +
  coord_flip()

Control bar width with `width`

The width argument of the geom_bar() function allows to control the bar width. It ranges between 0 and 1, 1 being full width.

See how this can be used to make bar charts with variable width.

# Load ggplot2
library(ggplot2)

# Create data
data <- data.frame(
  name=c("A","B","C","D","E") ,  
  value=c(3,12,5,18,45)
  )

# Barplot
ggplot(data, aes(x=name, y=value)) + 
  geom_bar(stat = "identity", width=0.2)

What’s next?

This post was an overview of ggplot2 barplots, showing the basic options of geom_barplot(). Visit the barplot section for more:

how to reorder your barplot
how to use variable bar width
what about error bars
circular barplots

Contact

This document is a work by Yan Holtz. Any feedback is highly encouraged. You can fill an issue on Github, drop me a message on Twitter, or send an email pasting yan.holtz.data with gmail.com.

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Most basic barplot with geom_bar()