The **interquartile range** represents the difference between the first quartile (the 25th percentile) and the third quartile (the 75th percentile) of a dataset.

In simple terms, it measures the spread of the middle 50% of values.

IQR = Q3 – Q1

We can use the built-in **IQR()** function to calculate the interquartile range of a set of values in R:

IQR(x)

The following examples show how to use this function in practice.

**Example 1: Interquartile Range of a Vector**

The following code shows how to calculate the interquartile range of values in a vector:

#define vector x <- c(4, 6, 6, 7, 8, 12, 15, 17, 20, 21, 21, 23, 24, 27, 28) #calculate interquartile range of values in vector IQR(x) [1] 14.5

**Example 2: Interquartile Range of a Vector with Missing Values**

If your vector has missing values, be sure to specify **na.rm=TRUE** to ignore missing values when calculating the interquartile range:

#define vector with some missing values x <- c(4, 6, NA, 7, NA, NA, 15, 17, 20, 21, 21, 23, 24, 27, 28) #calculate interquartile range of values in vector IQR(x, na.rm=TRUE) [1] 10.25

**Example 3: Interquartile Range of Column in Data Frame**

The following code shows how to calculate the interquartile range of a specific column in a data frame:

#define data frame df <- data.frame(var1=c(1, 3, 3, 4, 5), var2=c(7, 7, 8, 3, 2), var3=c(3, 3, 6, 6, 8), var4=c(1, 1, 2, 8, 9)) #calculate interquartile range of 'var1' column IQR(df$var1) [1] 1

**Example 4: Interquartile Range of Several Columns in Data Frame**

The following code shows how to calculate the interquartile range of several columns in a data frame:

#define data frame df <- data.frame(var1=c(1, 3, 3, 4, 5), var2=c(7, 7, 8, 3, 2), var3=c(3, 3, 6, 6, 8), var4=c(1, 1, 2, 8, 9)) #calculate interquartile range of 'var1', 'var2', and 'var4' columns sapply(df[ , c('var1', 'var2', 'var4')], IQR) var1 var2 var4 1 4 7

**Additional Resources**

How to Find the Range in R

How to Calculate Standard Deviation in R

How to Interpret Interquartile Range

Interquartile Range vs. Standard Deviation: What’s the Difference?