Why Every Data Scientist Needs the janitor Package (2024)

Lessons from Will Hunting andMcGayver

In the world of data science, data cleaning is often seen as one of the most time-consuming and least glamorous tasks. Yet, it’s also one of the most critical. Without clean data, even the most sophisticated algorithms and models can produce misleading results. This is where the janitor package in R comes into play, serving as the unsung hero that quietly handles the nitty-gritty work of preparing data for analysis.

Much like the janitors we often overlook in our daily lives, the janitor package works behind the scenes to ensure everything runs smoothly. It takes care of the small but essential tasks that, if neglected, could bring a project to a halt. The package simplifies data cleaning with a set of intuitive functions that are both powerful and easy to use, making it an indispensable tool for any data scientist.

To better understand the importance of janitor, we can draw parallels to two iconic figures from pop culture: Will Hunting, the genius janitor from Good Will Hunting, and McGayver, the handyman known for his ability to solve any problem with minimal resources. Just as Will Hunting and McGayver possess hidden talents that make a huge impact, the janitor package holds a set of powerful functions that can transform messy datasets into clean, manageable ones, enabling data scientists to focus on the more complex aspects of theirwork.

Will Hunting: The GeniusJanitor

Will Hunting, the protagonist of Good Will Hunting, is an unassuming janitor at the Massachusetts Institute of Technology (MIT). Despite his modest job, Will possesses a genius-level intellect, particularly in mathematics. His hidden talent is discovered when he solves a complex math problem left on a blackboard, something that had stumped even the brightest minds at the university. This revelation sets off a journey that challenges his self-perception and the expectations of those aroundhim.

The story of Will Hunting is a perfect metaphor for the janitor package in R. Just as Will performs crucial tasks behind the scenes at MIT, the janitor package operates in the background of data science projects. It handles the essential, albeit often overlooked, work of data cleaning, ensuring that data is in the best possible shape for analysis. Like Will, who is initially underestimated but ultimately proves invaluable, janitor is a tool that may seem simple at first glance but is incredibly powerful and essential for any serious data scientist.

Without proper data cleaning, even the most advanced statistical models can produce incorrect or misleading results. The janitor package, much like Will Hunting, quietly ensures that the foundations are solid, allowing the more complex and visible work toshine.

McGayver: The Handyman Who Fixes Everything

In your school days, you might have known someone who was a jack-of-all-trades, able to fix anything with whatever tools or materials were on hand. Perhaps this person was affectionately nicknamed “McGayver,” a nod to the famous TV character MacGyver, who was known for solving complex problems with everyday objects. This school janitor, like McGayver, was indispensable — working in the background, fixing leaks, unclogging drains, and keeping everything running smoothly. Without him, things would quickly fallapart.

This is exactly how the janitor package functions in the world of data science. Just as your school’s McGayver could solve any problem with a handful of tools, the janitor package offers a set of versatile functions that can clean up the messiest of datasets with minimal effort. Whether it’s removing empty rows and columns, cleaning up column names, or handling duplicates, janitor has a tool for the job. And much like McGayver, it accomplishes these tasks efficiently and effectively, often with a single line ofcode.

The genius of McGayver wasn’t just in his ability to fix things, but in how he could use simple tools to do so. In the same way, janitor simplifies tasks that might otherwise require complex code or multiple steps. It allows data scientists to focus on the bigger picture, confident that the foundations of their data aresolid.

Problem-Solving with and withoutjanitor

In this section, we’ll dive into specific data cleaning problems that data scientists frequently encounter. For each problem, we’ll first show how it can be solved using base R, and then demonstrate how the janitor package offers a more streamlined and efficient solution.

1. clean_names(): Tidying Up ColumnNames

Problem:
Column names in datasets are often messy — containing spaces, special characters, or inconsistent capitalization — which can make data manipulation challenging. Consistent, tidy column names are essential for smooth data analysis.

Base R Solution: To clean column names manually, you would need to perform several steps, such as converting names to lowercase, replacing spaces with underscores, and removing special characters. Here’s an example using baseR:

# Creating dummy empty data framedf = data.frame(a = NA, b = NA, c = NA, d = NA)# Original column namesnames(df) <- c("First Name", "Last Name", "Email Address", "Phone Number")# Cleaning the names manuallynames(df) <- tolower(names(df)) # Convert to lowercasenames(df) <- gsub(" ", "_", names(df)) # Replace spaces with underscoresnames(df) <- gsub("[^[:alnum:]_]", "", names(df)) # Remove special characters# Resulting column namesnames(df)# [1] "first_name" "last_name" "email_address" "phone_number"

This approach requires multiple lines of code, each handling a different aspect of cleaning.

janitor Solution: With the janitor package, the same result can be achieved with a single function:

# creating dummy empty data framedf = data.frame(a = NA, b = NA, c = NA, d = NA)names(df) <- c("First Name", "Last Name", "Email Address", "Phone Number")library(janitor)# Using clean_names() to tidy up column namesdf <- clean_names(df)# Resulting column namesnames(df)# [1] "first_name" "last_name" "email_address" "phone_number"

Why janitor Is Better: The clean_names() function simplifies the entire process into one step, automatically applying a set of best practices to clean and standardize column names. This not only saves time but also reduces the chance of making errors in your code. By using clean_names(), you ensure that your column names are consistently formatted and ready for analysis, without the need for manual intervention.

2. tabyl and adorn_ Functions: Creating Frequency Tables and Adding Totals or Percentages

Problem:
When analyzing categorical data, it’s common to create frequency tables or cross-tabulations. Additionally, you might want to add totals or percentages to these tables to get a clearer picture of your data distribution.

Base R Solution: Creating a frequency table and adding totals or percentages manually requires several steps. Here’s an example using baseR:

# Sample datadf <- data.frame( gender = c("Male", "Female", "Female", "Male", "Female"), age_group = c("18-24", "18-24", "25-34", "25-34", "35-44"))# Creating a frequency table using base Rtable(df$gender, df$age_group)# 18-24 25-34 35-44# Female 1 1 1# Male 1 1 0# Adding row totalsaddmargins(table(df$gender, df$age_group), margin = 1)# 18-24 25-34 35-44# Female 1 1 1# Male 1 1 0# Sum 2 2 1# Calculating percentagesprop.table(table(df$gender, df$age_group), margin = 1) * 100# 18-24 25-34 35-44# Female 33.33333 33.33333 33.33333# Male 50.00000 50.00000 0.00000

This method involves creating tables, adding margins manually, and calculating percentages separately, which can become cumbersome, especially with larger datasets.

janitor Solution: With the janitor package, you can create a frequency table and easily add totals or percentages using tabyl() and adorn_* functions:

# Sample datadf <- data.frame( gender = c("Male", "Female", "Female", "Male", "Female"), age_group = c("18-24", "18-24", "25-34", "25-34", "35-44"))library(janitor)# Piping all togethertable_df <- df %>% tabyl(gender, age_group) %>% adorn_totals("row") %>% adorn_percentages("row") %>% adorn_pct_formatting()table_df# gender 18-24 25-34 35-44# Female 33.3% 33.3% 33.3%# Male 50.0% 50.0% 0.0%# Total 40.0% 40.0% 20.0%

Why janitor Is Better: The tabyl() function automatically generates a clean frequency table, while adorn_totals() and adorn_percentages() easily add totals and percentages without the need for additional code. This approach is not only quicker but also reduces the complexity of your code. The janitor functions handle the formatting and calculations for you, making it easier to produce professional-looking tables that are ready for reporting or further analysis.

3. row_to_names(): Converting a Row of Data into ColumnNames

Problem:
Sometimes, datasets are structured with the actual column names stored in one of the rows rather than the header. Before starting the analysis, you need to promote this row to be the header of the dataframe.

Base R Solution: Without janitor, converting a row to column names can be done with the following steps using baseR:

# Sample data with column names in the first rowdf <- data.frame( X1 = c("Name", "John", "Jane", "Doe"), X2 = c("Age", "25", "30", "22"), X3 = c("Gender", "Male", "Female", "Male"))# Step 1: Extract the first row as column namescolnames(df) <- df[1, ]# Step 2: Remove the first row from the data framedf <- df[-1, ]# Resulting data framedf

This method involves manually extracting the row, assigning it as the header, and then removing the original row from thedata.

janitor Solution: With janitor, this entire process is streamlined into a single function:

# Sample data with column names in the first rowdf <- data.frame( X1 = c("Name", "John", "Jane", "Doe"), X2 = c("Age", "25", "30", "22"), X3 = c("Gender", "Male", "Female", "Male"))df <- row_to_names(df, row_number = 1)# Resulting data framedf

Why janitor Is Better: The row_to_names() function from janitor simplifies this operation by directly promoting the specified row to the header in one go, eliminating the need for multiple steps. This function is more intuitive and reduces the chance of errors, allowing you to quickly structure your data correctly and move on to analysis.

4. remove_constant(): Identifying and Removing Columns with ConstantValues

Problem:
In some datasets, certain columns may contain the same value across all rows. These constant columns provide no useful information for analysis and can clutter your dataset. Removing them is essential for streamlining yourdata.

Base R Solution: Identifying and removing constant columns without janitor requires writing a custom function or applying several steps. Here’s an example using baseR:

# Sample data with constant and variable columnsdf <- data.frame( ID = c(1, 2, 3, 4, 5), Gender = c("Male", "Male", "Male", "Male", "Male"), # Constant column Age = c(25, 30, 22, 40, 35))# Identifying constant columns manuallyconstant_cols <- sapply(df, function(col) length(unique(col)) == 1)# sapply() applies a function to each column in df.# The function checks if the length of unique values in a column is 1,# meaning the column is constant (all values are the same).# constant_cols will be a logical vector indicating which columns are constant.# Removing constant columnsdf <- df[, !constant_cols]# Resulting data framedf ID Age1 1 252 2 303 3 224 4 405 5 35

This method involves checking each column for unique values and then filtering out the constant ones, which can be cumbersome.

janitor Solution: With janitor, you can achieve the same result with a simple, one-line function:

df <- data.frame( ID = c(1, 2, 3, 4, 5), Gender = c("Male", "Male", "Male", "Male", "Male"), # Constant column Age = c(25, 30, 22, 40, 35))df <- remove_constant(df) ID Age1 1 252 2 303 3 224 4 405 5 35

Why janitor Is Better: The remove_constant() function from janitor is a straightforward and efficient solution to remove constant columns. It automates the process, ensuring that no valuable time is wasted on writing custom functions or manually filtering columns. This function is particularly useful when working with large datasets, where manually identifying constant columns would be impractical.

5. remove_empty(): Eliminating Empty Rows andColumns

Problem:
Datasets often contain rows or columns that are entirely empty, especially after merging or importing data from various sources. These empty rows and columns don’t contribute any useful information and can complicate data analysis, so they should beremoved.

Base R Solution: Manually identifying and removing empty rows and columns can be done, but it requires multiple steps. Here’s how you might approach it using baseR:

# Sample data with empty rows and columnsdf <- data.frame( ID = c(1, 2, NA, 4, 5), Name = c("John", "Jane", NA, NA,NA), Age = c(25, 30, NA, NA, NA), Empty_Col = c(NA, NA, NA, NA, NA) # An empty column)# Removing empty rowsdf <- df[rowSums(is.na(df)) != ncol(df), ]# rowSums(is.na(df)) checks if rows are entirely NA.# The result is a logical vector where TRUE indicates rows with some data.# Removing empty columnsdf <- df[, colSums(is.na(df)) != nrow(df)]# colSums(is.na(df)) checks if columns are entirely NA.# The result is a logical vector where TRUE indicates columns with some data.# Resulting data framedf ID Name Age1 1 John 252 2 Jane 304 4 NA5 5 NA

This method involves checking each row and column for completeness and then filtering out those that are entirely empty, which can be cumbersome and prone toerror.

janitor Solution: With janitor, you can remove both empty rows and columns in a single, straightforward functioncall:

# Sample data with empty rows and columnsdf <- data.frame( ID = c(1, 2, NA, 4, 5), Name = c("John", "Jane", NA, NA,NA), Age = c(25, 30, NA, NA, NA), Empty_Col = c(NA, NA, NA, NA, NA) # An empty column)df <- remove_empty(df, which = c("cols", "rows"))df ID Name Age1 1 John 252 2 Jane 304 4 <NA> NA5 5 <NA> NA

Why janitor Is Better: The remove_empty() function from janitor makes it easy to eliminate empty rows and columns with minimal effort. You can specify whether you want to remove just rows, just columns, or both, making the process more flexible and less error-prone. This one-line solution significantly simplifies the task and ensures that your dataset is clean and ready for analysis.

6. get_dupes(): Detecting and Extracting Duplicate Rows

Problem:
Duplicate rows in a dataset can lead to biased or incorrect analysis results. Identifying and managing duplicates is crucial to ensure the integrity of yourdata.

Base R Solution: Detecting and extracting duplicate rows manually can be done using base R with the following approach:

# Sample data with duplicate rowsdf <- data.frame( ID = c(1, 2, 3, 3, 4, 5, 5), Name = c("John", "Jane", "Doe", "Doe", "Alice", "Bob", "Bob"), Age = c(25, 30, 22, 22, 40, 35, 35))# Identifying duplicate rowsdupes <- df[duplicated(df) | duplicated(df, fromLast = TRUE), ]# Resulting data frame with duplicatesdupesID Name Age3 3 Doe 224 3 Doe 226 5 Bob 357 5 Bob 35

This approach uses duplicated() to identify duplicate rows. While it’s effective, it requires careful handling to ensure all duplicates are correctly identified and extracted, especially in more complex datasets.

janitor Solution: With janitor, identifying and extracting duplicate rows is greatly simplified using the get_dupes() function:

# Sample data with duplicate rowsdf <- data.frame( ID = c(1, 2, 3, 3, 4, 5, 5), Name = c("John", "Jane", "Doe", "Doe", "Alice", "Bob", "Bob"), Age = c(25, 30, 22, 22, 40, 35, 35))# Using get_dupes() to find duplicate rowsdupes <- get_dupes(df)# Resulting data frame with duplicatesdupes# It gives us additional info how many repeats of each row we have ID Name Age dupe_count1 3 Doe 22 22 3 Doe 22 23 5 Bob 35 24 5 Bob 35 2

Why janitor Is Better: The get_dupes() function from janitor not only identifies duplicate rows but also provides additional information, such as the number of times each duplicate appears, in an easy-to-read format. This functionality is particularly useful when dealing with large datasets, where even a straightforward method like duplicated() can become cumbersome. With get_dupes(), you gain a more detailed and user-friendly overview of duplicates, ensuring the integrity of yourdata.

7. round_half_up, signif_half_up, and round_to_fraction: Rounding Numbers with Precision

Problem:
Rounding numbers is a common task in data analysis, but different situations require different types of rounding. Sometimes you need to round to the nearest integer, other times to a specific fraction, or you might need to ensure that rounding is consistent in cases like 5.5 rounding up to6.

Base R Solution: Rounding numbers in base R can be done using round() or signif(), but these functions don't always handle edge cases or specific requirements like rounding half up or to a specific fraction:

# Sample datanumbers <- c(1.25, 2.5, 3.75, 4.125, 5.5)# Rounding using base R's round() functionrounded <- round(numbers, 1) # Rounds to one decimal place# Rounding to significant digits using signif()significant <- signif(numbers, 2)# Resulting rounded valuesrounded[1] 1.2 2.5 3.8 4.1 5.5significant[1] 1.2 2.5 3.8 4.1 5.5

While these functions are useful, they may not provide the exact rounding behavior you need in certain situations, such as consistently rounding half values up or rounding to specific fractions.

janitor Solution: The janitor package provides specialized functions like round_half_up(), signif_half_up(), and round_to_fraction() to handle these cases with precision:

# Using round_half_up() to round numbers with half up logicrounded_half_up <- round_half_up(numbers, 1)# Using signif_half_up() to round to significant digits with half up logicsignificant_half_up <- signif_half_up(numbers, 2)# Using round_to_fraction() to round numbers to the nearest fractionrounded_fraction <- round_to_fraction(numbers, denominator = 4)rounded_half_up[1] 1.3 2.5 3.8 4.1 5.5significant_half_up[1] 1.3 2.5 3.8 4.1 5.5rounded_fraction[1] 1.25 2.50 3.75 4.00 5.50

Why janitor Is Better: The janitor functions round_half_up(), signif_half_up(), and round_to_fraction() offer more precise control over rounding operations compared to base R functions. These functions are particularly useful when you need to ensure consistent rounding behavior, such as always rounding 5.5 up to 6, or when rounding to the nearest fraction (e.g., quarter or eighth). This level of control can be critical in scenarios where rounding consistency affects the outcome of an analysis orreport.

8. chisq.test() and fisher.test(): Simplifying Hypothesis Testing

Problem:
When working with categorical data, it’s often necessary to test for associations between variables using statistical tests like the Chi-squared test (chisq.test()) or Fisher’s exact test (fisher.test()). Preparing your data and setting up these tests manually can be complex, particularly when dealing with larger datasets with multiple categories.

Base R Solution: Here’s how you might approach this using a more complex dataset with baseR:

# Sample data with multiple categoriesdf <- data.frame( Treatment = c("A", "A", "B", "B", "C", "C", "A", "B", "C", "A", "B", "C"), Outcome = c("Success", "Failure", "Success", "Failure", "Success", "Failure", "Success", "Success", "Failure", "Failure", "Success", "Failure"), Gender = c("Male", "Female", "Male", "Female", "Male", "Female", "Male", "Female", "Male", "Female", "Male", "Female"))# Creating a contingency tablecontingency_table <- table(df$Treatment, df$Outcome, df$Gender)# Performing Chi-squared test (on a 2D slice of the table)chisq_result <- chisq.test(contingency_table[,, "Male"])# Performing Fisher's exact test (on the same 2D slice)fisher_result <- fisher.test(contingency_table[,, "Male"])# Resultschisq_result Pearson's Chi-squared testdata: contingency_table[, , "Male"]X-squared = 2.4, df = 2, p-value = 0.3012fisher_result Fisher's Exact Test for Count Datadata: contingency_table[, , "Male"]p-value = 1alternative hypothesis: two.sided

This approach involves creating a multidimensional contingency table and then slicing it to apply the tests. This can become cumbersome and requires careful management of the data structure.

janitor Solution: Using janitor, you can achieve the same results with a more straightforward approach:

# Sample data with multiple categoriesdf <- data.frame( Treatment = c("A", "A", "B", "B", "C", "C", "A", "B", "C", "A", "B", "C"), Outcome = c("Success", "Failure", "Success", "Failure", "Success", "Failure", "Success", "Success", "Failure", "Failure", "Success", "Failure"), Gender = c("Male", "Female", "Male", "Female", "Male", "Female", "Male", "Female", "Male", "Female", "Male", "Female"))library(janitor)# Creating a tabyl to perform Chi-squared and Fisher's exact tests for Male participantsdf_male <- df %>% filter(Gender == "Male") %>% tabyl(Treatment, Outcome)# Performing Chi-squared testchisq_result <- chisq.test(df_male)# Performing Fisher's exact testfisher_result <- fisher.test(df_male)# Resultschisq_result Pearson's Chi-squared testdata: df_maleX-squared = 2.4, df = 2, p-value = 0.3012fisher_result Fisher's Exact Test for Count Datadata: df_malep-value = 1alternative hypothesis: two.sided

Why janitor Is Better: The janitor approach simplifies the process by integrating the creation of contingency tables (tabyl()) with the execution of hypothesis tests (chisq.test() and fisher.test()). This reduces the need for manual data slicing and ensures that the data is correctly formatted for testing. This streamlined process is particularly advantageous when dealing with larger, more complex datasets, where manually managing the structure could lead to errors. The result is a faster, more reliable workflow for testing associations between categorical variables.

The Unsung Heroes of DataScience

In both the physical world and the realm of data science, there are tasks that often go unnoticed but are crucial for the smooth operation of larger systems. Janitors, for example, quietly maintain the cleanliness and functionality of buildings, ensuring that everyone else can work comfortably and efficiently. Without their efforts, even the most well-designed spaces would quickly descend intochaos.

Similarly, the janitor package in R plays an essential, yet often underappreciated, role in data science. Data cleaning might not be the most glamorous aspect of data analysis, but it’s undoubtedly one of the most critical. Just as a building cannot function properly without regular maintenance, a data analysis project cannot yield reliable results without clean, well-prepared data.

The functions provided by the janitor package — whether it’s tidying up column names, removing duplicates, or simplifying complex rounding tasks — are the data science equivalent of the work done by janitors and handymen in the physical world. They ensure that the foundational aspects of your data are in order, allowing you to focus on the more complex, creative aspects of analysis and interpretation.

Reliable data cleaning is not just about making datasets look neat; it’s about ensuring the accuracy and integrity of the insights derived from that data. Inaccurate or inconsistent data can lead to flawed conclusions, which can have significant consequences in any field — from business decisions to scientific research. By automating and simplifying the data cleaning process, the janitor package helps prevent such issues, ensuring that the results of your analysis are as robust and trustworthy as possible.

In short, while the janitor package may work quietly behind the scenes, its impact on the overall success of data science projects is profound. It is the unsung hero that keeps your data — and, by extension, your entire analysis — on solidground.

Throughout this article, we’ve delved into how the janitor package in R serves as an indispensable tool for data cleaning, much like the often-overlooked but essential janitors and handymen in our daily lives. By comparing its functions to traditional methods using base R, we’ve demonstrated how janitor simplifies and streamlines tasks that are crucial for any data analysisproject.

The story of Will Hunting, the genius janitor, and the analogy of your school’s “McGayver” highlight how unnoticed figures can make extraordinary contributions with their unique skills. Similarly, the janitor package, though it operates quietly in the background, has a significant impact on data preparation. It handles the nitty-gritty tasks — cleaning column names, removing duplicates, rounding numbers precisely — allowing data scientists to focus on generating insights and buildingmodels.

We also explored how functions like clean_names(), tabyl(), row_to_names(), remove_constants(), remove_empty(), get_dupes(), and round_half_up() drastically reduce the effort required to prepare your data. These tools save time, ensure data consistency, and minimize errors, making them indispensable for any data professional.

Moreover, we emphasized the critical role of data cleaning in ensuring reliable analysis outcomes. Just as no building can function without the janitors who maintain it, no data science workflow should be without tools like the janitor package. It is the unsung hero that ensures your data is ready for meaningful analysis, enabling you to trust your results and make sound decisions.

In summary, the janitor package is more than just a set of utility functions — it’s a crucial ally in the data scientist’s toolkit. By handling the essential, behind-the-scenes work of data cleaning, janitor helps ensure that your analyses are built on a solid foundation. So, if you haven’t already integrated janitor into your workflow, now is the perfect time to explore its capabilities and see how it can elevate your data preparation process.

Consider adding janitor to your R toolkit today. Explore its functions and experience firsthand how it can streamline your workflow and enhance the quality of your data analysis. Your data — and your future analyses — will thankyou.

Why Every Data Scientist Needs the janitor Package was originally published in Numbers around us on Medium, where people are continuing the conversation by highlighting and responding to this story.

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