Working with Dplyr’s Anti Join: Passing Argument Values into the By Condition
In this article, we will delve into the world of data manipulation using R and the popular dplyr library. Specifically, we will explore how to use the anti_join function from dplyr and pass argument values into its by condition.
Introduction to Dplyr’s Anti Join
The anti_join function in dplyr is used to perform an anti join on two data frames. An anti join is a type of merge operation that returns all rows from one or both data frames where the join condition is not met. In other words, it returns all rows from one data frame that do not have a match in the other data frame.
The basic syntax for using anti_join is:
anti_join(df1, df2, by = c("column1" = "column2"))
This tells dplyr to perform an anti join on df1 and df2 based on the equality of column1 and column2.
Passing Argument Values into the By Condition
In your question, you are trying to pass argument values from a command line script into the by condition in anti_join. The default format is:
anti_join(df1, df2, by = c("a" = "b"))
You want to substitute the values of a and b with the argument values received from the command line script.
To achieve this, you can use the !!sym() function from dplyr’s rlang package, which allows you to convert a symbol (in this case, an expression containing argument names) into an expression that can be used in the by condition.
Using the rlang Package
First, you need to install and load the rlang package:
install.packages("rlang")
library(rlang)
Then, you can use !!sym() to convert your argument names into expressions:
a.id <- c("EMP_CLIENT_ID")
b.id <- c("VEND_CLIENT_ID")
# Convert a.id and b.id into expressions using !!sym()
expr_a_id <- !!sym(a.id)
expr_b_id <- !!sym(b.id)
# Now you can use these expressions in the by condition:
anti_join(Src_df, Tgt_df, by = c(expr_a_id = expr_b_id))
By using !!sym(), you are essentially telling dplyr to substitute the values of a.id and b.id into the by condition.
Using R’s Command Line Argument Parsing
If you’re working with a command line script, you can use R’s built-in function commandArgs() to access the argument names. Here’s an example:
# Load necessary libraries
require(dplyr)
require(rlang)
# Get the argument names from commandArgs()
a_id <- commandArgs()[1]
b_id <- commandArgs()[2]
# Convert a.id and b.id into expressions using !!sym()
expr_a_id <- !!sym(a_id)
expr_b_id <- !!sym(b_id)
# Now you can use these expressions in the by condition:
anti_join(Src_df, Tgt_df, by = c(expr_a_id = expr_b_id))
In this example, commandArgs()[1] and commandArgs()[2] return the first and second argument names passed to your script, respectively.
Additional Considerations
When working with dplyr’s anti join, it’s essential to keep in mind that this operation returns all rows from one data frame where the join condition is not met. If you’re dealing with large datasets, this can result in a significant amount of data being returned.
To mitigate this issue, you may want to consider using distinct() or group_by() before performing the anti join, depending on your specific use case.
Conclusion
In this article, we explored how to use dplyr’s anti_join function and pass argument values into its by condition. We covered using the rlang package to convert argument names into expressions, as well as R’s command line argument parsing capabilities.
By following these steps, you should be able to effectively use dplyr’s anti join with custom arguments from your command line script.
Example Use Cases
- Anti Join with Custom Arguments
Load necessary libraries
require(dplyr) require(rlang)
Create example data frames
df1 <- data.frame(a = c(“EMP_CLIENT_ID”, “VEND_CLIENT_ID”), b = c(10, 20)) df2 <- data.frame(c = c(“EMP_CLIENT_ID”, “VEND_CLIENT_ID”), d = c(30, 40))
Get argument names from commandArgs()
a_id <- commandArgs()[1] b_id <- commandArgs()[2]
Convert a.id and b.id into expressions using !!sym()
expr_a_id <- !!sym(a_id) expr_b_id <- !!sym(b_id)
Perform anti join with custom arguments
result <- anti_join(df1, df2, by = c(expr_a_id = expr_b_id))
Print result
print(result)
* **Anti Join without Custom Arguments**
```markdown
# Load necessary libraries
require(dplyr)
# Create example data frames
df1 <- data.frame(a = c("EMP_CLIENT_ID", "VEND_CLIENT_ID"), b = c(10, 20))
df2 <- data.frame(c = c("EMP_CLIENT_ID", "VEND_CLIENT_ID"), d = c(30, 40))
# Perform anti join without custom arguments
result <- anti_join(df1, df2, by = c("a" = "c"))
# Print result
print(result)
- Anti Join with Distinct
Load necessary libraries
require(dplyr)
Create example data frames
df1 <- data.frame(a = c(“EMP_CLIENT_ID”, “VEND_CLIENT_ID”), b = c(10, 20)) df2 <- data.frame(c = c(“EMP_CLIENT_ID”, “VEND_CLIENT_ID”), d = c(30, 40))
Perform anti join with distinct
result <- anti_join(df1, df2, by = c(“a” = “c”)) %>% distinct(a)
Print result
print(result)
* **Anti Join with Group By**
```markdown
# Load necessary libraries
require(dplyr)
# Create example data frames
df1 <- data.frame(a = c("EMP_CLIENT_ID", "VEND_CLIENT_ID"), b = c(10, 20))
df2 <- data.frame(c = c("EMP_CLIENT_ID", "VEND_CLIENT_ID"), d = c(30, 40))
# Perform anti join with group by
result <- anti_join(df1, df2, by = c("a" = "c")) %>%
group_by(a)
# Print result
print(result)
Last modified on 2023-10-02