# Find the frequency of unique values for each column in an R data frame.

To find the frequency of unique values for each column in an R data frame, we can use apply function with table function.

For Example, if we have a data frame called df then we can find the frequency of unique values for each column in df by using the below mentioned command −

apply(df,2,table)

## Example 1

Following snippet creates a sample data frame −

x1<-sample(c(2,5,7,4),20,replace=TRUE)
x2<-sample(c(2,5,7,4),20,replace=TRUE)
x3<-sample(c(2,5,7,4),20,replace=TRUE)
df1<-data.frame(x1,x2,x3)
df1

The following dataframe is created

  x1 x2 x3
1 2 5  7
2 5 4  5
3 5 5  5
4 5 4  4
5 5 5  2
6 5 7  7
7 7 7  2
8 2 2  2
9 4 4  7
10 2 5  5
11 2 4  4
12 5 7  5
13 2 5  4
14 2 5  4
15 5 5  7
16 5 5  4
17 5 7  5
18 2 4  4
19 7 7  5
20 5 5  7

To find the frequency of unique values for each column in df1 on the above created data frame, add the following code to the above snippet −

x1<-sample(c(2,5,7,4),20,replace=TRUE)
x2<-sample(c(2,5,7,4),20,replace=TRUE)
x3<-sample(c(2,5,7,4),20,replace=TRUE)
df1<-data.frame(x1,x2,x3)
apply(df1,2,table)

## Output

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

  x1 x2 x3
2  7 1 3
4  1 5 6
5 10 9 6
7  2 5 5

## Example 2

Following snippet creates a sample data frame −

y1<-rpois(20,1)
y2<-rpois(20,1)
y3<-rpois(20,1)
df2<-data.frame(y1,y2,y3)
df2

The following dataframe is created

  y1 y2 y3
1 3 1  1
2 4 0  1
3 1 2  4
4 0 3  1
5 2 0  1
6 2 0  0
7 2 1  1
8 3 2  0
9 2 0  0
10 1 0  2
11 1 3  0
12 2 1  0
13 1 1  2
14 0 3  2
15 0 2  2
16 0 0  1
17 2 1  2
18 4 2  1
19 0 1  4
20 0 0  3

To find the frequency of unique values for each column in df2 on the above created data frame, add the following code to the above snippet −

y1<-rpois(20,1)
y2<-rpois(20,1)
y3<-rpois(20,1)
df2<-data.frame(y1,y2,y3)
apply(df2,2,table)

## Output

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

$y1 0 1 2 3 4 6 4 6 2 2$y2
0 1 2 3
7 6 4 3
\$y3
0 1 2 3 4
5 7 5 1 2

## Example 3

Following snippet creates a sample data frame −

z1<-sample(0:4,20,replace=TRUE)
z2<-sample(0:4,20,replace=TRUE)
z3<-sample(0:4,20,replace=TRUE)
df3<-data.frame(z1,z2,z3)
df3

The following dataframe is created

 z1 z2 z3
1 2 2 1
2 4 1 3
3 1 3 4
4 4 4 1
5 0 0 3
6 0 4 3
7 3 1 3
8 4 1 1
9 3 4 3
10 3 4 1
11 4 4 0
12 2 4 0
13 3 1 4
14 3 3 1
15 4 3 1
16 0 2 3
17 3 3 2
18 3 4 2
19 0 3 0
20 4 4 4

To find the frequency of unique values for each column in df3 on the above created data frame, add the following code to the above snippet −

z1<-sample(0:4,20,replace=TRUE)
z2<-sample(0:4,20,replace=TRUE)
z3<-sample(0:4,20,replace=TRUE)
df3<-data.frame(z1,z2,z3)
apply(df3,2,table)

## Output

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

 z1 z2 z3
0 4 1  3
1 1 4  6
2 2 2  2
3 7 5  6
4 6 8  3