# Remove rows from a data frame that exists in another data frame in R.

To remove rows from a data frame that exists in another data frame, we can use subsetting with single square brackets. This removal will help us to find the unique rows in the data frame based on the column of another data frame.

Check out the below Examples to understand how it can be done.

## Example 1

Following snippet creates a sample data frame −

x<-rpois(20,2)
y<-rpois(20,2)
df1<-data.frame(x,y)
df1

The following dataframe is created

   x y
1  2 0
2  1 2
3  1 3
4  2 1
5  0 0
6  3 3
7  1 3
8  0 2
9  3 2
10 2 0
11 2 1
12 1 6
13 1 2
14 2 1
15 4 5
16 2 2
17 1 4
18 0 1
19 0 1
20 2 2

Add the following code to the above snippet −

x<-rpois(20,2)
y<-rpois(20,2)
df1<-data.frame(x,y)
a<-rpois(20,5)
b<-rpois(20,5)
df2<-data.frame(a,b)
df2

The following dataframe is created

   a b
1  4 0
2  3 6
3  4 6
4  1 3
5  5 3
6  5 7
7  5 2
8  4 6
9  4 6
10 4 3
11 3 6
12 4 4
13 4 2
14 5 2
15 4 3
16 3 7
17 4 6
18 5 3
19 3 3
20 9 3

To remove rows in df1 based on column x that do not exist in column a of df2 on the above created data frame, add the following code to the above snippet −

x<-rpois(20,2)
y<-rpois(20,2)
df1<-data.frame(x,y)
a<-rpois(20,5)
b<-rpois(20,5)
df2<-data.frame(a,b)
df1[!df1$x %in% df2$a,]


## Output

If you execute all the above given snippets as a single program, it generates the following Output −

   x y
1  2 0
4  2 1
5  0 0
8  0 2
10 2 0
11 2 1
14 2 1
16 2 2
18 0 1
19 0 1
20 2 2

## Example 2

Following snippet creates a sample data frame −

Grp<-sample(LETTERS[1:5],20,replace=TRUE)
Rate<-rpois(20,5)
df_grp<-data.frame(Grp,Rate)
df_grp

The following dataframe is created

 Grp Rate
1  D 6
2  D 3
3  E 7
4  D 6
5  B 6
6  D 3
7  D 3
8  A 3
9  C 2
10 A 4
11 A 7
12 C 7
13 C 5
14 E 7
15 B 7
16 C 6
17 B 6
18 A 4
19 C 6
20 B 1

Add the following code to the above snippet −

Grp<-sample(LETTERS[1:5],20,replace=TRUE)
Rate<-rpois(20,5)
df_grp<-data.frame(Grp,Rate)
Category<-sample(LETTERS[3:7],20,replace=TRUE)
Sales<-rpois(20,10)
df_Sales<-data.frame(Category,Sales)
df_Sales

The following dataframe is created

Category Sales
1    E    12
2    C    11
3    D     9
4    E    13
5    G     5
6    C     9
7    D    14
8    D    11
9    D     8
10   F    11
11   F    17
12   G    15
13   F    12
14   D     9
15   G    13
16   C     9
17   C    12
18   F     7
19   E     7
20   C     8

To remove rows in df_grp based on column Grp that do not exist in column Category of df_Sales on the above created data frame, add the following code to the above snippet −

Grp<-sample(LETTERS[1:5],20,replace=TRUE)
Rate<-rpois(20,5)
df_grp<-data.frame(Grp,Rate)
Category<-sample(LETTERS[3:7],20,replace=TRUE)
Sales<-rpois(20,10)
df_Sales<-data.frame(Category,Sales)
df_grp[!df_grp$Grp %in% df_Sales$Category,]

## Output

If you execute all the above given snippets as a single program, it generates the following Output −

Grp  Rate
5  B 6
8  A 3
10 A 4
11 A 7
15 B 7
17 B 6
18 A 4
20 B 1