How to plot histograms in R

A histogram is a category of bar chart that shows numerical data distribution. It provides a visual representation of the frequency of data. A histogram consists of vertical bars, while the height of each bar in the histogram corresponds to several items in that category or bin. The range of each bucket or category is user-defined.

They are beneficial when there is a lot of data to analyze and difficult to draw conclusions or data demographics. The histogram is used in various fields such as Data Science, Machine, and deep learning. The most popular use for histograms is in market research, where they can determine the potential demand for a product or service.

Histograms in R programming language

R provides programmers the ability to create histograms so that they can easily visualize and analyze the trends in the abundance of data they are working with. Now that we know what histograms are, and how they can be used let us see how they can be created in R programming.

hist() function in R

hist() function is used to create a histogram in R. The syntax of this function is as follows:

Syntax

hist(v, main, xlab, xlim, ylim, breaks, col, border)

Parameters

The following is a description of all the parameters used in the hist() function.

• v: Vector containing the numerical values ​​used to create the histogram.
• main: Indicates the name of the graph.
• col: It will set the fill color of the bars.
• border: Used to set the border color of each bar.
• xlab: Used to describe the x-axis.
• xlim: Specify the range of values ​​on the x-axis.
• ylim: Specify the range of values ​​on the y-axis.
• breaks: Indicate the width of each bar or the number of bars in the chart.

However, not all the parameters are mandatory. Programmers can create histograms using a combination of these parameters.

Return Value

The hist() method calculates the histogram of the given data. If it can be plotted, it creates an object of the class histogram which is first plotted and then returned.

Explanation

Following are some examples that clarify how to create histograms in R using some or all the parameters of the hist() function.

Histograms Using Only Input Vector

The simplest way to create a histogram in R is by only providing the input vector v to the hist() function.

# create data for the graph containing weights in kg
weights <- c(75, 80, 85, 82, 81, 82, 76, 79, 73, 85, 74, 76, 86, 72, 75)
# create the histogram.
hist(weights)

• Line#2: declares the input vector weight using c() function.
• Line#4: calls the hist() function which plots the histogram using the given vector.

Output

We get the following histogram as output.

Histograms With Colored Borders

# Create data for the graph containing weights in kg
weights <- c(75, 80, 85, 82, 81, 82, 76, 79, 73, 85, 74, 76, 86, 72, 75)
# Create the histogram.
hist(weights, col = "green", border = "black")

• Line#4: Calls the hist() function but this time, it also defines the fill and border color of the histogram bars by using the col and border parameters respectively.

Output

We get a histogram given below

Histograms With Description

We can also alter the label of the x-axis of our histogram using the xlab parameter in the hist() function. By default, the description is the name of your input vector.

# Create data for the graph containing weights in kg
weights <- c(75, 80, 85, 82, 81, 82, 76, 79, 73, 85, 74, 76, 86, 72, 75)
# Create the histogram.
hist(weights, xlab="Weights in KG", col = "blue", border = "red")

• Line#4: In addition to calling the hist() function, also declares the description of the histogram using the xlab parameter which is set to Weights in KG.

Output

The output histogram is attached below. Notice that the label on x-axis has changed to the one provided in hist() using xlab parameter.

Histograms With Range and Breaks

We can specify the range of the x and y-axis as well as the number of rectangles in our histogram using the xlim, ylim, and breaks parameters.

# Create data for the graph containing weights in kg
weights <- c(75, 80, 85, 82, 81, 82, 76, 79, 73, 85, 74, 76, 86, 72, 75)
# Create the histogram.
hist(weights, xlab="Weights in KG", col = "green", border = "black", xlim = c (70, 90), ylim = c(0, 3), breaks = 10)

Line#4: the range of the x-axis and y-axis has been declared using the xlim and ylim parameters. The breaks parameter is also set to 10  which sets the number of bars in the histogram to 10.

Output

Following is the resulting histogram