Histogram in R Programming

The Histogram in R Programming is very useful to visualize the statistical information, that is organized in user specified bins (range, or breaks). Though it looks like Barplot, Histograms display data in equal intervals. In this article we will show you, How to Create a Histogram, Remove it Axes, Format its color, adding labels, adding the density curves, and drawing multiple Histograms in R Programming language with example.

Syntax of a Histogram in R

The basic syntax to draw the Histogram in R Programming is as shown below

and the complex syntax behind this Histogram is:

Before we get into the example, let us the see the data that we are going to use for this Histogram example. airquality is the date set provided by the R

Return Value of a Histogram in R Programming

In general, before we start creating a Histogram, let us see how the data is divided by the histogram. Histogram will return the frequency (count), density, bin (breaks) values, and type of graph. In this example we will show you, How to get the information of the same

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Create a Histogram in R Programming

In this example we will show you, How to create a Histogram using the airquality data set, which is provided by the R Studio. If your requirement is to import data from external files then, I suggest you to refer R Read CSV article to understand the csv file import

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OUTPUT

ANALYSIS

airquality data set will return the output as a List. So, we are using the $ to extract the data from List.

Assigning names to Histogram in R Programming

In this example we will show you, How to assign names to Histogram, X-Axis, and Y-Axis using main, xlab, and ylab

• main: You can change, or provide the Title for your Histogram.
• xlab: Please specify the label for the X-Axis
• ylab: Please specify the label for the Y-Axis
• las: It is used to change the Y axis values direction

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Change Colors of a Histogram in R

In this example we will show you, How to change the Histogram color using col argument

• col: Please specify the color you want to use for your Histogram. Type colors() in your console to get the list of colors available in R programming

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From the above code snippet you can observe that, we used two colors for the col argument. It means, those two colors will be repeated until the end of bars.

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Removing Axis and Adding labels to Histogram in R

In this example we will show you, How to remove the X-Axis, Y-Axis, and how to assign labels to each bar in histogram using axes, ann, and labels argument.

• axes: It is a Boolean argument. If it is TRUE, axis is drawn.
• labels: It is a Boolean argument. If it is TRUE, Histogram will return the value of each bar on top it.
• ann: It is a Boolean argument. If it is FALSE, Histogram will remove the annotations from the plot area, which includes Histogram name, Axis Names.

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Change Axis limits of a Histogram in R

In this example we will show you, How to change the default axis values, and also changing the bar density using density argument

• xlim: This argument can help you to specify the limits for the X-Axis
• ylim: This argument may help you to specify the Y-Axis limits. In this example, We are changing the default y-axis values (0, 35) to (0, 40)
• density: Please specify the shading lines density (in lines per inch). By default it is NULL,  means no shading lines.

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Changing Bins of a Histogram in R

In this example we will show you, How to change the Bin size using breaks argument

• You can use a Vector of values that specify the break points between histogram cells.
• You can use a Number that specify the number of cells a histogram has to return. For example, breaks = 20 means, 20 bars will be returned.
• You can use a function that returns a Vector of break points.

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Create a R Histogram with Density

Frequency will count and give us the number of data points per bin. In real-time we are more interested in density than the frequency based histograms because, density can give the probability densities. In this example we will show you, How to create a Histogram against the Density and to achieve the same, we have set the freq argument to FALSE.

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Adding Density Curve to Histogram in R

In this example we will show you, How to add the density curve to the Histogram using lines function.

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ANALYSIS

Following statement will draw a density curve

TIP: lwd argument is used to change the width of the line

Add Multiple Histograms in R

In this example we will show you, How to add multiple Histogram to plot region.

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Creating R Histogram using CSV File

In this example we will show you, How to create a Histogram using the external data. For this, we are importing data from the csv file using read.csv function. I suggest you to refer R Read CSV article to understand the steps involved in csv file import

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Above code snippet will draw the histogram for the Sales Amount

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