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Piping in R Programming

  • Dec 26, 2023
  • 7 Minutes Read
Piping in R Programming

The piping mechanism is one of the main components that allows R to have a concise, readable, and expressive code. In this article, we will look at the R %>% operator and the Magrittr package. We will explore these packages and operators in-depth and learn how they work together to improve and streamline data analysis and manipulation.

Understanding the Basics

Let us first start by learning about the basics before we dig into the more advanced and complex techniques. Piping is a method that lets us chain multiple operations together in a step-by-step sequence. It helps create a well-defined path/pipeline for the data to flow through, transforming itself as per our requirements and necessities. This improves the code's readability and offers a clear method for understanding how data transformations are carried out. So, understanding how piping works is helpful in making more expressive and complex data transformations and manipulation in our code.

What is the Magrittr Package?

The Magrittr package is a fundamental building block for implementing piping in R. It introduces the %>% operator in R, which is commonly known as the pipe operator. 

To get started with Magrittr, you can install it using the following command.

install.packages("magrittr")

 

Once installed, we can load the package into our R environment by running the following code.

library(magrittr)

 

You can use the %>% operator to pipe data from one operation to another when using Magrittr. This helps in making a more readable code and reduces the need for intermediate variables.

What is the %>% Operator?

The %>% operator is the foundation of the piping mechanism in R. It takes the output of one function and passes it as the first argument to the next function. Doing this creates a streamlined workflow, where data flows through our sequence of operations.

Let us look at a simple example to illustrate the working of the %>% operator.

Code:

result <- sqrt(sum(1:10))


result_piped <- 1:10 %>% sum() %>% sqrt()

 

Output:

[1] 7.416198

 

In this example, the %>% operator takes the output of 1:10 and pipes it to the sum() function. The result of sum() is then passed to the sqrt() function. This chaining of operations helps enhance the code readability and reduces the need for complicated nested function calls.

Building Blocks of Piping

To take full advantage of piping, it is necessary to understand the fundamental building blocks that the Magrittr package has to offer. These consist of various operators and functions that enhance the flexibility and expressiveness of coding in addition to the standard %>% operator.

1. Forward Pipe Operator %>%

The primary operator, %>%, is used for forward piping. It receives the value from its left and sends it to the function from its right as the first argument. This makes it easier for data to flow naturally from one step to the next.

result <- data_frame %>% filter(column > 10) %>% summarise(mean_value = mean(column))

 

In this example, data_frame is passed to the filter() function, and the result is then passed to the summarise() function. A summarised data frame based on the given conditions is the final product.

2. The Dot Placeholder .

You can use the dot placeholder (.) to refer to the outcome of the pipeline's previous step. This is particularly helpful if you wish to apply a function to the outcome of an earlier operation.

result <- data_frame %>% filter(column > 10) %>% summarise(mean_value = mean(., na.rm = TRUE))

 

Here, the dot placeholder is used within the mean() function to reference the result of the filter() operation.

3. Exposition using %$%

The %$% operator is intended specifically for exposing variables within a data frame, whereas %>% is used for function calls. It enables direct reference to a data frame's columns.

result <- data_frame %>% filter(column > 10) %$% mean(column, na.rm = TRUE)

 

Here, the column is referenced directly within the mean() function, simplifying the code.

4. Pipe to Assignment with %<>%

The %<>% operator can be used in situations where you wish to change an object while it is still in place. This is especially helpful when updating an object iteratively.

vector %<>% sort() %>% unique()

 

In this example, the %<>% operator modifies the original vector in place by sorting it and removing duplicates.

Applications of Piping

Now that we have a strong foundation in piping in R, let's explore some practical applications where Magrittr and the %>% operator sign.

1. Data Wrangling with dplyr

The dplyr package, part of the tidyverse ecosystem, complements the Magrittr package. It offers a selection of functions that have been designed for managing data. These features help make the data manipulation easy and readable when paired with piping.

library(dplyr)

result <- iris %>%
  filter(Species == "setosa") %>%
  group_by(Species) %>%
  summarise(mean_sepal_length = mean(Sepal.Length))

 

In this example, data is grouped by a particular column, rows are filtered using the %>% operator, and the mean sepal length for each species is then determined. The code makes it simple to follow because it reads like a set of steps.

2. Chaining Custom Functions

Piping can easily integrate with your custom functions as well as the built-in ones, increasing the versatility of your code. Assume you have two functions that you wish to use in order: train_model() and preprocess_data(), let's have a look at the code on how to do this.

result <- raw_data %>%
  preprocess_data() %>%
  train_model()

 

This method promotes code reuse and increases the versatility of the code. It is possible to independently develop, test, and maintain each function.

3. Improved Readability in Nested Operations

Imagine a situation where you have to do nested operations, such as calculating the square root of the sum of squares of a vector. Without piping, this could appear confusing and difficult to handle.

result <- sqrt(sum((vector)^2))

 

With piping, the code becomes more intuitive.

result_piped <- vector %>% 
  raise_to_power(2) %>% 
  sum() %>% 
  sqrt()

 

Here, each step in the computation is clearly separated, making the code more readable and reducing the chance of errors.

Conclusion

Piping in R is a transformative data analysis and manipulation tool made possible by the Magrittr package and the %>% operator. It improves the readability, expressiveness, and versatility of code, making it a vital tool for R programmers. By mastering the fundamentals of Magrittr, discovering the flexibility of %>%, and following best practices, you can write code that is easier to read, write, and maintain. Learning to use tools like Magrittr will enable you to approach complex analyses efficiently and confidently as you navigate the ever-changing field of data science, opening up new avenues for data manipulation and exploration.

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About The Author
Abhisek Ganguly
Passionate machine learning enthusiast with a deep love for computer science, dedicated to pushing the boundaries of AI through academic research and sharing knowledge through teaching.