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R Plotting - Bar Chart

A bar chart, also known as a bar graph, is a statistical graph that uses the length of rectangular bars to represent variables.

Bar charts can be horizontal or vertical, and each bar can have a different color.

In R, the barplot() function is used to create bar charts, with the following format:

barplot(H, xlab, ylab, main, names.arg, col, beside)

Parameter descriptions:

H: A vector or matrix containing numeric values used in the chart, where each value represents the height of a bar.
xlab: The label for the x-axis.
ylab: The label for the y-axis.
main: The title of the chart.
names.arg: The names for each bar.
col: The color for each bar.

Next, we create a simple bar chart:

Example

# Prepare a vector
cvd19 = c(83534, 2640626, 585493)

# Display the bar chart
barplot(cvd19)

Executing the plotting program will generate a PDF file (Rplots.pdf) in the current directory. Opening the file will show the graphical output as follows:

To better convey information, we can add a title, colors, and names for each bar on the chart.

Below, we create a bar chart showing the number of COVID-19 cases in China, the USA, and India on July 1, 2020.

Chinese characters require setting the font parameter family='GB1':

Example

cvd19 = c(83534, 2640626, 585493)

barplot(cvd19,
    main="COVID-19 Bar Chart",
    col=c("#ED1C24", "#22B14C", "#FFC90E"),
    names.arg=c("China", "USA", "India"),
    family='GB1'
)

The data in barplot can be either a vector or a matrix. Now, we generate a bar chart comparing COVID-19 cases in June and July.

First, prepare the data:

	China	USA	India
June	83017	1794546	190535
July	83534	2640626	585493

Convert to a matrix, generate the bar chart, and display in a side-by-side format with color samples.

Here, we set our own font library. For details, refer to R Plotting - Chinese Support.

Example

library(showtext);
font_add("SyHei", "SourceHanSansSC-Bold.otf");
cvd19 = matrix(
  c(83017, 83534, 1794546, 2640626, 190535, 585493),
  2, 3
)

# Set file name, output as png
png(file = "tutorialpro-bar-1.png")

# Load font
showtext_begin();

colnames(cvd19) = c("China", "USA", "India")
rownames(cvd19) = c("June", "July")
barplot(cvd19, main = "COVID-19 Bar Chart", beside=TRUE, legend=TRUE,  family='SyHei')

# Remove font
showtext_end();

The following code will generate a tutorialpro-bar-1.png file in the current program directory, as shown below:

We set the color samples to be for each group:

Example

library(plotrix)
library(showtext);
font_add("SyHei", "SourceHanSansSC-Bold.otf");
cvd19 = matrix(
  c(83017, 83534, 1794546, 2640626, 190535, 585493),
  2, 3
)

# Set file name, output as png
png(file = "tutorialpro-bar-2.png")
# Load font
showtext_begin();
colnames(cvd19) = c("China", "USA", "India")
rownames(cvd19) = c("June", "July")

barplot(cvd19, main = "COVID-19 Bar Chart", beside=TRUE, legend=TRUE, col=c("blue", "green"),  family='SyHei')
# Remove font
showtext_end();

The following code will generate a tutorialpro-bar-2.png file in the current program directory, as shown below:

beside Parameter

The beside parameter sets the stacking method for the bars, with the default being FALSE:

beside=FALSE: The heights of the bars are the values of the matrix, and the bars are stacked horizontally.

beside=TRUE: The heights of the bars are the values of the matrix, and the bars are displayed side by side.

library(showtext);
font_add("SyHei", "SourceHanSansSC-Bold.otf");
cvd19 = matrix(
  c(83017, 83534, 1794546, 2640626, 190535, 585493),
  2, 3
)

# Set file name, output as png
png(file = "tutorialpro-bar-3.png")
# Load font
showtext_begin();
colnames(cvd19) = c("China", "USA", "India")
rownames(cvd19) = c("June", "July")

barplot(cvd19, main = "COVID-19 Bar Chart", beside=FALSE, legend=TRUE, col=c("blue","green"), family='SyHei')
# Remove font
showtext_end();

The following code will generate a tutorialpro-bar-3.png file in the current program directory, as shown below:

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