*12*

The **setdiff()** function in R can be used to find differences between two sets. This function uses the following syntax:

**setdiff(x, y)**

where:

**x, y:**Vectors or data frames containing a sequence of items

This tutorial provides several examples of how to use this function in practice.

**Example 1: Setdiff with Numeric Vectors**

The following code shows how to useÂ **setdiff()** to identify all of the values in vector *a* that do not occur in vectorÂ *b*:

#define vectors a #find all values inathat do not occur inbsetdiff(a, b) [1] 9 10

There are two values that occur in vectorÂ *a* that do not occur in vectorÂ *b*:Â **9** andÂ **10**.

If we reverse the order of the vectors in theÂ **setdiff()** function, we can instead identify all of the values in vectorÂ *b* that do not occur in vectorÂ *a*:

#find all values inbthat do not occur inasetdiff(b, a) [1] 2 6

There are two values that occur in vectorÂ *b* that do not occur in vectorÂ *a*: **2** and **6**.

**Example 2: Setdiff with Character Vectors**

The following code shows how to useÂ **setdiff()** to identify all of the values in vector *char1* that do not occur in vector *char2*:

#define character vectors char1 #find all values inchar1that do not occur inchar2setdiff(char1, char2) [1] "C" "D"

**Example 3: Setdiff with Data Frames**

The following code shows how to useÂ **setdiff()** to identify all of the values in one data frame column that do not appear in the same column of a second data frame:

#define data frames df1 frame(team=c('A', 'B', 'C', 'D'), conference=c('West', 'West', 'East', 'East'), points=c(88, 97, 94, 104)) df2 frame(team=c('A', 'B', 'C', 'D'), conference=c('West', 'West', 'East', 'East'), points=c(88, 97, 98, 99)) #find differences between the points columns in the two data frames setdiff(df1$points, df2$points) [1] 94 104

We can see that the valuesÂ **94** andÂ **104** occur in the points column of the first data frame, but not in the points column of the second data frame.

**Additional Resources**

How to Sum Specific Columns in R

How to Sum Specific Rows in R

How to Perform Partial String Matching in R