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The post How to Find Unmatched Records in R appeared first on Data Science Tutorials

How to Find Unmatched Records in R?, To retrieve all rows in one data frame that do not have matching values in another data frame, use the anti_join() function from the dplyr package in R.

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The following is the fundamental syntax for this function.

`anti_join(df1, df2, by='col_name')`

The examples below demonstrate how to utilise this syntax in practise.

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## Example 1: Use anti join() with One Column

Let’s pretend we have the following two R data frames:

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```df1 <- data.frame(team=c('A', 'B', 'C', 'D', 'E'),
points=c(102, 104, 129, 224, 436))
df2 <- data.frame(team=c('A', 'B', 'C', 'F', 'G'),
points=c(412, 514, 519, 233, 117))```

To return all rows in the first data frame that do not have a matching team in the second data frame, we can use the anti_join() function.

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`library(dplyr)`

Using the ‘team’ column, execute an anti-join.

```anti_join(df1, df2, by='team')
team points
1    D    224
2    E    436```

We can see that in the second data frame, there are exactly two teams from the first data frame that do not have a corresponding team name.

## Example 2: Use anti_join() with Multiple Columns

Let’s pretend we have the following two R data frames.

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Let’s create the data frames

```df1 <- data.frame(team=c('A', 'A', 'A', 'B', 'B', 'B'),
position=c('G', 'G', 'F', 'G', 'F', 'C'),
points=c(182, 164, 159, 124, 136, 441))
df2 <- data.frame(team=c('A', 'A', 'A', 'B', 'B', 'B'),
position=c('G', 'G', 'C', 'G', 'F', 'F'),
points=c(152, 154, 159, 322, 217, 522))```

The anti_join() method can be used to return all rows in the first data frame that do not match a team or position in the second data frame.

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`library(dplyr)`

Use the ‘team’ and ‘position’ columns to do an anti-join.

```anti_join(df1, df2, by=c('team', 'position'))
team position points
1    A        F    159
2    B        C    441```

We can see that in the second data frame, there are exactly two records from the first data frame that do not have a corresponding team name and position.

The post How to Find Unmatched Records in R appeared first on Data Science Tutorials