What are bar plots in R programming?
A bar plot displays data in rectangular bars, with the lengths of the bars proportional to the value of the variable. R uses the barplot() subroutine to generate bar plots. R generates both types of bar plots, vertical and horizontal. You can pass different arguments to customize the barplot() function.
Syntax
The prototype of the barplot() function is as follows:
barplot(h, xlab, ylab, main, names.arg, col)
Parameters
The barplot() function accepts the following parameters:
h: a matrix that contains numeric values of the chartxlab: a tag for the x-axisylab: a tag for the y-axismain: the title for bar plotnames.arg: a vector of labels that appear in each barcol: specifies the colors of the bars
Examples
Bar plot without title or tags
The code below plots a simple bar plot. We pass the data vector as an argument to the barplot() method to generate a graph.
# Create the data for the chartdata <- c(8,13,26,3,43,21)# Give the chart file a namepng(file = "barplot.png")# Plot the bar chartbarplot(data)
Bar plot with title and tags
In this example, the bar plot contains x and y labels, as well as a graph name. The code below plots a graph that represents the population of different states in the United States.
# Create the datadata <- c(8,13,26,3,43,21)labels <- c("Calif.", "Colo.", "Wash.", "Fla.", "Ga.", "Tex.")# Plotbarplot(data, xlab= "States", ylab = "Population in 1000s", main="Population Chart",names.arg = labels, col ="red", border = "yellow")# Give a name to filepng(file = "US_States.png")
Note: The
png(file = "US_States.png")command saves the bar plot as a file namedUS_States.png.
Types of bar plots in R
R programming offers multiple types of bar plots, such as:
- Simple colored bar plot
- Horizontal bar plot
- Bar plot with labels
- Stacked bar plot with legend
- Grouped bar plot with legend
1. Simple colored bar plot
The code below plots a simple bar plot. We pass the data vector as an argument to the barplot() method to generate a blue graph.
# Create datadata <- c(0.2, 0.75, 0.2, 0.4, 0.5)barplot(data, col = "#3375FF")# Give a name to filepng(file = "graph.png")
2. Horizontal bar plot
To plot the graph horizontally, the horiz parameter must be set to TRUE, as shown below:
# Horizontal barplotsdata <- c(0.2, 0.65, 0.3, 0.4, 0.5)barplot(data, horiz = TRUE)# Give a name to filepng(file = "graph.png")
3. Bar plot with labels
Each bar can also be given a specific name or label by setting the names.arg attribute equal to the desired bar labels, e.g., labels <- LETTERS[1:6].
The LETTERS[1:6] command generates English letters from A to F, as shown below:
# Create grouping variabledata <- c(0.2, 0.65, 0.3, 0.4, 0.5,0.8)labels <- LETTERS[1:6]# Add labelsbarplot(data, names.arg =labels)# Give a name to filepng(file = "graph.png")
4. Stacked bar plot with a legend
To generate a stacked bar plot with a legend, you can use the legend() method with specific parameters, as shown below:
# Create matrix for stacked barplotdata <- as.matrix(data.frame(A = c(0.9, 1.2), B = c(0.6, 0.3), C = c(0.6, 0.3), D = c(0.4, 0.4), E = c(0.3, 0.1), F = c(0.3, 0.1)))# Create stacked barplotbarplot(data, col = c("#3375FF", "#494B4F"))# Add legendlegend("topright", legend = c("Covid Patients", "Pneumonia Patients"), fill = c("#3375FF", "#494B4F"))# Give a name to filepng(file = "graph.png")
5. Grouped bar plot with a legend
Grouped bar plots can be used to compare multiple instances together. The code below compares rounds of soccer matches between Bolivia and Paraguay.
data <- as.matrix(data.frame(R1 = c(0.9, 1.2), R2 = c(0.6, 0.3), R3 = c(0.6, 0.3), R4 = c(0.4, 0.4), R5 = c(0.3, 0.1)))# Create grouped barplotbarplot(data, col = c("#FF3333", "#3375FF"), beside = TRUE)# Add legendlegend("topright", legend = c("Bolivia", "Paraguay"), fill = c("#FF3333", "#3375FF"))# Give a name to filepng(file = "graph.png")
