Set values in categorical column to numeric values in R data frame.

To set values in categorical column to numeric values in R data frame, we can use combine function c.

For Example, if we have a data frame called df that contains a categorical column say C which has two categories as Low and High and if we want to represent these categories with 1 and 10 then we can use the below command −

df$C<-c(Low=1,High=10)[df$C]

Example 1

Following snippet creates a sample data frame −

Group<-sample(c("First","Second","Third"),20,replace=TRUE)
df1<-data.frame(Group)
df1

The following dataframe is created

   Group
1  Third
2  Second
3  First
4  Second
5  Second
6  First
7  Third
8  Third
9  First
10 Second
11 First
12 First
13 First
14 Second
15 First
16 First
17 First
18 Second
19 Second
20 Third

To replace values in Group column to numeric on the above created data frame, add the following code to the above snippet −

Group<-sample(c("First","Second","Third"),20,replace=TRUE)
df1<-data.frame(Group)
df1$Group<-c(First=1,Second=2,Third=3)[df1$Group]
df1

Output

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

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

Example 2

Following snippet creates a sample data frame −

Level<-sample(c("Low","Medium","High"),20,replace=TRUE)
df2<-data.frame(Level)
df2

The following dataframe is created

   Level
1  Medium
2  Low
3  Low
4  High
5  Medium
6  Medium
7  Medium
8  Medium
9  Low
10 Low
11 Low
12 Low
13 Low
14 High
15 Medium
16 Medium
17 Low
18 Low
19 Medium
20 Medium

To replace values in Level column to numeric on the above created data frame, add the following code to the above snippet −

Level<-sample(c("Low","Medium","High"),20,replace=TRUE)
df2<-data.frame(Level)
df2$Level<-c(Low=5,Medium=15,High=20)[df2$Level]
df2

Output

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

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