Quick Tips for Data Cleaning in R

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What to Expect

I’m excited to share pro-tips that will expedite your process for cleaning and standardizing column names in your data; this is a critical yet sometimes overlooked step in the cleaning + tidying of data.

There are a couple of handy functions() available in R to help effectively execute these tasks.

By the end of this short article you’ll have a couple of new tricks up your sleeve for getting those column names just the way you want them 😎

Data Wrangling Toolkit 🧰

  • The clean_names() function from the janitor library.
  • The set_names() function from the purrr library.

Load our Libraries

library(tidyverse)      # Work-Horse Package
library(tidytuesdayR)   # Access Data from Tidy Tuesday
library(janitor)        # Data Cleaning Package
library(purrr)          # Functional Programming Toolkit

Let’s Get Some Data

I’m grabbing a couple of data-sets from the Tidy Tuesday Project that will help us walk through a couple of examples together.

# Get Marine Mammal Data
cetacean_week    <- tidytuesdayR::tt_load("2018-12-18")
cetacean_raw_tbl <- cetacean_week$allCetaceanData 

# Get NFL Salary Data
nfl_salary_week    <- tidytuesdayR::tt_load("2018-04-09")
nfl_salary_raw_tbl <- nfl_salary_week$nfl_salary

Each of these data-sets contain column naming useful for emphasizing the value in the aforementioned functions.

Let’s start with the janitor library and it’s nifty function called clean_names().

Janitor Makes Life Easy

My head exploded 🤯 when learning about the Janitor library - it’s one of my favorite’s and I use the clean_names() function ALL the time.

Standardizing our naming convention upfront in our data cleaning pipeline can save enormous amounts of time downstream. I’m a big fan of the 🐍 snake_case 🐍 naming convention and so I typically like the columns of my data to follow that pattern.

Fortunately, the janitor::clean_names() function has built in functionality to programmatically clean up our column names - my favorite part is that by default it favors the snake_case naming convention.

Let’s Look at an Example

Pulling a few columns from our marine-mammal data we see that our columns are not in our preferred snake_case convention.

# Get subset of columns for example
cetacean_subset_tbl <- cetacean_raw_tbl %>% 
    # Select columns using helper_functions()
    select(contains("origin"), contains("date"), COD)

# Transpose Data to view Column Names
## Rows: 2,194
## Columns: 6
## $ originDate      1989-04-07, 1973-11-26, 1978-05-13, 1979-02-03, 1979-…
## $ originLocation  "Marineland Florida", "Dolphin Research Center", "SeaW…
## $ statusDate      NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, N…
## $ transferDate    NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, N…
## $ entryDate       1989-04-07, 1973-11-26, 1978-05-13, 1979-02-03, 1979-…
## $ COD             NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA…

Mixed Naming, Let’s Standardize

As you can see we’ve got columns in lowerCamel and also in UPPERCASE. To standardize, let’s now use the clean_names() function to tidy these up.

# Clean up Column Names + Glimpse Output
cetacean_subset_tbl %>% 
    clean_names() %>% 
## Rows: 2,194
## Columns: 6
## $ origin_date      1989-04-07, 1973-11-26, 1978-05-13, 1979-02-03, 1979…
## $ origin_location  "Marineland Florida", "Dolphin Research Center", "Sea…
## $ status_date      NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, …
## $ transfer_date    NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, …
## $ entry_date       1989-04-07, 1973-11-26, 1978-05-13, 1979-02-03, 1979…
## $ cod              NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, N…

Those Column Names Look Great!

Now imagine you have a picky partner/colleague who insists on a format like ALLCAPS - you’ve tried to convince them otherwise but they insist 🙄

# Standardize Column Naming - ALLCAPS
cetacean_cols_allcaps_tbl <- cetacean_subset_tbl %>% 
    clean_names(case = "all_caps")

# Glimpse Output
cetacean_cols_allcaps_tbl %>% glimpse()
## Rows: 2,194
## Columns: 6
## $ ORIGIN_DATE      1989-04-07, 1973-11-26, 1978-05-13, 1979-02-03, 1979…
## $ ORIGIN_LOCATION  "Marineland Florida", "Dolphin Research Center", "Sea…
## $ STATUS_DATE      NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, …
## $ ENTRY_DATE       1989-04-07, 1973-11-26, 1978-05-13, 1979-02-03, 1979…
## $ COD              NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, N…


Nice way to be a team-player 👍

Next Example: set_names()

With clean_names() in our tool bag, we can now combine it with set_names() to programmatically standardize ALL of our column names using advanced techniques.

Let’s take a quick peak at the columns from the NFL Salary data.

nfl_salary_raw_tbl %>% names() 
##  [1] "year"              "Cornerback"        "Defensive Lineman"
##  [4] "Linebacker"        "Offensive Lineman" "Quarterback"      
##  [7] "Running Back"      "Safety"            "Special Teamer"   
## [10] "Tight End"         "Wide Receiver"

Now imagine instead of requiring snake_case, the columns need to be lower-case with a dash instead of an underscore in between words.

The set_names() function allows us to Set the Names of a Vector programmatically.

Using the names() function above, we can pass a vector of our column names and manipulate each name in similar fashion.

Let’s look at an example.

nfl_salary_raw_tbl %>% 
    clean_names() %>% 
##  [1] "year"              "cornerback"        "defensive_lineman"
##  [4] "linebacker"        "offensive_lineman" "quarterback"      
##  [7] "running_back"      "safety"            "special_teamer"   
## [10] "tight_end"         "wide_receiver"

We’ve effectively used clean_names() to quickly clean up our column names.

However, we still need to replace those underscores with dashes.

Check this out 😎

nfl_salary_raw_tbl %>% 
    clean_names() %>% 
    set_names(names(.) %>% str_replace_all("_", "-")) %>% 
## Rows: 800
## Columns: 11
## $ year                 2011, 2011, 2011, 2011, 2011, 2011, 2011, 2011, 2…
## $ cornerback           11265916, 11000000, 10000000, 10000000, 10000000,…
## $ `defensive-lineman`  17818000, 16200000, 12476000, 11904706, 11762782,…
## $ linebacker           16420000, 15623000, 11825000, 10083333, 10020000,…
## $ `offensive-lineman`  15960000, 12800000, 11767500, 10358200, 10000000,…
## $ quarterback          17228125, 16000000, 14400000, 14100000, 13510000,…
## $ `running-back`       12955000, 10873833, 9479000, 7700000, 7500000, 70…
## $ safety               8871428, 8787500, 8282500, 8000000, 7804333, 7652…
## $ `special-teamer`     4300000, 3725000, 3556176, 3500000, 3250000, 3225…
## $ `tight-end`          8734375, 8591000, 8290000, 7723333, 6974666, 6133…
## $ `wide-receiver`      16250000, 14175000, 11424000, 11415000, 10800000,…

I learned this trick in the Data Science for Business 101 course taught by Matt Dancho.

At first, I was puzzled by the names(.) component and didn’t understand what the period was doing. In the course I learned that using the dot (.) enables passing the incoming tibble to multiple-spots in the function.

set_names() is a vectorized function and so the first argument is a vector. The dot functionality in R allows us to take the incoming tibble and pass it to the names(.) function. Once we have the names in a vector we use the str_replace_all() function to replace the underscore with a dash.

The str_replace_all() function uses regular expression pattern matching and so the options are endless for how creative you can get here.


That’s it for today!

We used clean_names() and set_names() to effectively standardize our column naming conventions.

Get the code here: Github Repo.

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