Histogram in R Programming

The Histogram in R Programming is very useful to visualize the statistical information that organized in user-specified bins (range, or breaks). Though it looks like Barplot, Histograms in R display data in equal intervals, please refer Barplot article.

Let us see how to Create a Histogram in R, Remove it Axes, Format its color, adding labels, adding the density curves, and drawing multiple Histograms in R Programming language with example.

Histogram in R Syntax

The syntax to draw the Histogram in R Programming is

hist(x, col = NULL, main = NULL, xlab = xname, ylab)

and the complex syntax behind this R Histogram is:

hist(x, breaks = "Sturges", freq = NULL, probability = !freq,
     xlim = range(breaks), ylim = NULL, col = NULL, angle = 45,
     include.lowest = TRUE, right = TRUE, density = NULL, 
     main = NULL, xlab = xname, ylab, border = NULL,  
     axes = TRUE, plot = TRUE, labels = FALSE, 
     nclass = NULL, warn.unused = TRUE,..)

Before we get into the example, let us 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 divided by the histogram.

The Histogram in R returns the frequency (count), density, bin (breaks) values, and type of graph. In this example, we show how to get the information on the same

# R Histogram Data
airquality

return_Value <- hist(airquality$Temp)
return_Value

OUTPUT

Create a Histogram in R Programming

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

# Create a R Histogram
airquality

hist(airquality$Temp)

OUTPUT

ANALYSIS

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

hist(airquality$Temp)

Assigning names to Histogram in R Programming

In this example, we 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: Used to change the Y-axis values direction

# R Histogram Example - Changing Axis Names
airquality

hist(airquality$Temp,
     main = "Temperature Histogram",
     xlab = "Temperature",
     ylab = "Temperature Frequency",
     las = 1
     )

OUTPUT

Change Colors of a Histogram in R

In this example, we change the Histogram color using the 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

# R Histogram Example - Changing Colors
airquality

hist(airquality$Temp,
     main = "Temperature Histogram",
     xlab = "Temperature",
     ylab = "Temperature Frequency",
     las = 1,
     col = c("skyblue", "chocolate2")
     )

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

Remove Axis and Adding labels to Histogram in R

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

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

# R Histogram Example - Removing Axis Labels
airquality

return_Value <- hist(airquality$Temp)
return_Value

hist(airquality$Temp,
     axes = FALSE,
     ann = FALSE,
     labels = TRUE,
     ylim = c(0, 35),
     col = c("skyblue", "chocolate2")
     )

OUTPUT

Change Axis limits of a Histogram

Let us change the default axis values, and also changing the bar density using density argument of R histogram

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.

# R Histogram Example - Changing Axis Values
airquality

return_Value <- hist(airquality$Temp)
return_Value

hist(airquality$Temp,
     main = "Temperature Histogram",
     xlab = "Temperature",
     ylab = "Temperature Frequency",
     las = 1,
     col = c("skyblue", "chocolate2"),
     xlim = c(55, 100),
     ylim = c(0, 40), 
     density = 80
     )

OUTPUT

Changing Bins of a Histogram

Let us see how to change the Bin size of R histogram using breaks argument.

You can use a Vector of values that specify the breakpoints between histogram cells.
You can use a number that specifies the number of cells a histogram has to return. For example, breaks = 20 means 20 bars returned.
You can use a function that returns a Vector of breakpoints.

# R Histogram Example - Changing Bins
airquality

return_Value <- hist(airquality$Temp)
return_Value

hist(airquality$Temp,
     breaks = 20,
     main = "Temperature Histogram",
     xlab = "Temperature",
     ylab = "Temperature Frequency",
     las = 1,
     col = c("skyblue", "chocolate2"),
     labels = TRUE,
     ylim = c(0, 25)
     )

OUTPUT

Create a R Histogram with Density

Frequency counts and gives 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 create a Histogram in R against the Density, and to achieve the same, we have set the freq argument to FALSE.

# R Histogram Example - Density Values
airquality

return_Value <- hist(airquality$Temp)
return_Value

hist(airquality$Temp,
     freq = FALSE,
     main = "Temperature Histogram",
     xlab = "Temperature",
     ylab = "Temperature Density",
     las = 1,
     col = c("skyblue", "chocolate2")
     )

OUTPUT

Adding Density Curve to Histogram

In this example, we add the density curve to the Histogram in R programming using lines function.

# R Histogram Example - Add Density Curve
airquality

hist(airquality$Temp,
     freq = FALSE,
     main = "Temperature Histogram",
     xlab = "Temperature",
     ylab = "Temperature Density",
     las = 1,
     col = c("skyblue", "chocolate2")
     )

lines(density(airquality$Temp), lwd = 4, col = "red")

OUTPUT

ANALYSIS

The following statement draws a density curve

lines(density(airquality$Temp), lwd = 4, col = "red")

TIP: lwd argument change the width of the line

Add Multiple Histograms in R

In this example, we add multiple Histograms to plot region.

# R Histogram Example - Multiple Histograms
airquality

# Drawing Histogram for all the temperature values, where Month Number  = 7
hist(airquality$Temp[airquality$Month == 7],
     main = "Multiple Histograms",
     xlab = "Temperature",
     ylab = "Temperature Frequency",
     las = 1,
     breaks = 20,
     col = "skyblue",
     labels = T
     )

# Drawing Histogram for all the temperatures, where Month Number  = 8
hist(airquality$Temp[airquality$Month == 8],
     add = TRUE,
     col = "chocolate2",
     breaks = 20,
     labels = T
     )

OUTPUT

Creating R Histogram using CSV File

Let us see how to create a Histogram in R using the external data. For this, we are importing data from the CSV file using read.csv function. Please refer R Read CSV article.

# R Histogram Example - CSV File

employee <- read.csv("Products.csv", TRUE, sep = ",", 
                     na.strings = TRUE)

employee$SalesAmount

hist(employee$SalesAmount,
     main = "Sales Histogram",
     xlab = "Sale Amount",
     ylab = "Sales Frequency",
     las = 1,
     col = "skyblue"
     )

The above code snippet draws the histogram in R using the CSV file for the Sales Amount.

OUTPUT