R: How to Merge Data Frames by Column Names

You can use the following methods to merge data frames by column names in R:

Method 1: Merge Based on One Matching Column Name

merge(df1, df2, by='var1')

Method 2: Merge Based on One Unmatched Column Name

merge(df1, df2, by.x='var1', by.y='variable1')

Method 3: Merge Based on Multiple Matching Column Names

merge(df1, df2, by=c('var1', 'var2'))

Method 4: Merge Based on Multiple Unmatched Column Names

merge(df1, df2, by.x=c('var1', 'var2'), by.y=c('variable1', 'variable2'))

The following examples show how to use each method in practice.

Example 1: Merge Based on One Matching Column Name

The following code shows how to merge two data frames in R based on one matching column name:

#define data frames
df1 <- data.frame(team=c('A', 'B', 'C', 'D'),
                  points=c(88, 98, 104, 100))

df2 <- data.frame(team=c('A', 'B', 'C', 'D'),
                  rebounds=c(22, 31, 29, 20))

#merge based on one column with matching name
merge(df1, df2, by='team')

  team points rebounds
1    A     88       22
2    B     98       31
3    C    104       29
4    D    100       20

The result is one data frame that matched rows in each data frame using the team column.

Example 2: Merge Based on One Unmatched Column Name

The following code shows how to merge two data frames in R based on one unmatched column name:

#define data frames
df1 <- data.frame(team=c('A', 'B', 'C', 'D'),
                  points=c(88, 98, 104, 100))

df2 <- data.frame(team_name=c('A', 'B', 'C', 'D'),
                  rebounds=c(22, 31, 29, 20))

#merge based on one column with unmatched name
merge(df1, df2, by.x='team', by.y='team_name')

  team points rebounds
1    A     88       22
2    B     98       31
3    C    104       29
4    D    100       20

The result is one data frame that matched rows using the team column in the first data frame and the team_name column in the second data frame.

Example 3: Merge Based on Multiple Matching Column Names

The following code shows how to merge two data frames in R based on multiple matching column names:

#define data frames
df1 <- data.frame(team=c('A', 'A', 'B', 'B'),
                  position=c('G', 'F', 'G', 'F'),
                  points=c(88, 98, 104, 100))

df2 <- data.frame(team=c('A', 'A', 'B', 'B'),
                  position=c('G', 'F', 'G', 'F'),
                  rebounds=c(22, 31, 29, 20))

#merge based on multiple columns with matching names
merge(df1, df2, by=c('team', 'position'))

  team position points rebounds
1    A        F     98       31
2    A        G     88       22
3    B        F    100       20
4    B        G    104       29

The result is one data frame that matched rows in each data frame using the team and position column in each data frame.

Example 4: Merge Based on Multiple Unmatched Column Names

The following code shows how to merge two data frames in R based on multiple unmatched column names:

#define data frames
df1 <- data.frame(team=c('A', 'A', 'B', 'B'),
                  position=c('G', 'F', 'G', 'F'),
                  points=c(88, 98, 104, 100))

df2 <- data.frame(team_name=c('A', 'A', 'B', 'B'),
                  position_name=c('G', 'F', 'G', 'F'),
                  rebounds=c(22, 31, 29, 20))

#merge based on multiple columns with matching names
merge(df1, df2, by.x=c('team', 'position'), by.y=c('team_name', 'position_name'))

  team position points rebounds
1    A        F     98       31
2    A        G     88       22
3    B        F    100       20
4    B        G    104       29

The result is one data frame that matched rows using the team and position columns in the first data frame and the team_name and position_name columns in the second data frame.