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.
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$Temp) return_Value
Create a Histogram in R Programming
In this example, we create a Histogram using the airquality data set, which is provided by the Studio. If you require import data from external files, then I suggest you refer to R Read CSV article to understand the CSV file import. And also refer Barplot article in R Programming.
# Create a R Histogram airquality hist(airquality$Temp)
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
)
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$Temp,
main = "Temperature Histogram",
xlab = "Temperature",
ylab = "Temperature Frequency",
las = 1,
col = c("skyblue", "chocolate2")
)
From the above code snippet, you can observe that we used two colors for the col argument. It means those two colors repeated until the end of bars.
Remove Axis and Adding labels to Histogram
In this example, we remove the X-Axis, Y-Axis, and how to assign labels to each bar in the histogram using axes, ann, and labels argument.
- axes: It is a Boolean argument. If it is TRUE, the axis is drawn.
- labels: It is a Boolean argument. If it is TRUE, Histogram returns the value on top of each bar.
- ann: It is a Boolean argument. If it is FALSE, Histogram removes the annotations from the plot area, which includes the Histogram name, Axis Names.
# R Histogram Example - Removing Axis Labels
airquality
return_Value <- hist(airquality$Temp)
return_Value
hist(airquality$Temp,
axes = FALSE,
ann = FALSE,
labels = TRUE,
ylim = c(0, 35),
col = c("skyblue", "chocolate2")
)
Change Axis limits of a Histogram
Let us change the default axis values, and also changing the bar density using density argument of R histogram
- xlim: This argument can help you to specify the limits for the X-Axis
- ylim: This argument may help you to specify the Y-Axis limits. In this example, we are changing the default y-axis values (0, 35) to (0, 40)
- density: Please specify the shading lines density (in lines per inch). By default it is NULL, means no shading lines.
# R Histogram Example - Changing Axis Values
airquality
return_Value <- hist(airquality$Temp)
return_Value
hist(airquality$Temp,
main = "Temperature Histogram",
xlab = "Temperature",
ylab = "Temperature Frequency",
las = 1,
col = c("skyblue", "chocolate2"),
xlim = c(55, 100),
ylim = c(0, 40),
density = 80
)
Changing Bins of a Histogram
Let us see how to change the Bin size of R histogram using breaks argument.
- You can use a Vector of values that specify the breakpoints between histogram cells.
- You can use a number that specifies the number of cells a histogram has to return. For example, breaks = 20 means 20 bars returned.
- You can use a function that returns a Vector of breakpoints.
# R Histogram Example - Changing Bins
airquality
return_Value <- hist(airquality$Temp)
return_Value
hist(airquality$Temp,
breaks = 20,
main = "Temperature Histogram",
xlab = "Temperature",
ylab = "Temperature Frequency",
las = 1,
col = c("skyblue", "chocolate2"),
labels = TRUE,
ylim = c(0, 25)
)
Create a R Histogram with Density
Frequency counts and gives us the number of data points per bin. In real-time, we are more interested in density than the frequency-based histograms because density can give the probability densities.
In this example, we create a Histogram in R against the Density, and to achieve the same, we have set the freq argument to FALSE.
# R Histogram Example - Density Values
airquality
return_Value <- hist(airquality$Temp)
return_Value
hist(airquality$Temp,
freq = FALSE,
main = "Temperature Histogram",
xlab = "Temperature",
ylab = "Temperature Density",
las = 1,
col = c("skyblue", "chocolate2")
)
Adding Density Curve to Histogram
In this example, we add the density curve to the Histogram in R programming using lines function.
# R Histogram Example - Add Density Curve
airquality
hist(airquality$Temp,
freq = FALSE,
main = "Temperature Histogram",
xlab = "Temperature",
ylab = "Temperature Density",
las = 1,
col = c("skyblue", "chocolate2")
)
lines(density(airquality$Temp), lwd = 4, col = "red")
The following statement draws a density curve
lines(density(airquality$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
)
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 using the CSV file for the Sales Amount.
