Many tidyverse users turn to the tidyr R package for reshaping data. But I’ve seen people say they can’t remember exactly how its pivot_wider() and pivot_longer() functions work. Luckily, there’s an easy solution: RStudio code snippets. Write a snippet once, and what’s basically a fill-in-the-blank form will always be at your fingertips.
From wide to longTo go from wide to long with tidyr, use the pivot_longer() function. It has the following syntax:pivot_longer(mydata, cols, # columns that should pivot from wide to long (unquoted)names_to, # name of the new category column as a quoted stringvalues_to # name of the new value column as a quoted string)For a simple example, let’s look at the well-known mtcars data set, which has a wide format. It doesn’t have a column category at all — models are row names but not in their own variable — so I used the tibble package’s handy rownames_to_column() function to add a Model column from the row names:library(tibble)library(tidyr)mtcars <- tibble::rownames_to_column(mtcars, “Model”)head(mtcars)
Model mpg cyl disp hp drat wt qsec vs am gear carb
1 Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
2 Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
3 Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
4 Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
5 Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
6 Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1To convert mtcars into “tidy” or long format, all the columns starting from mpg to the last one (carb) should shift into just two new columns — one for category and another for value:mtcars_long <- pivot_longer(mtcars,cols = mpg:carb,names_to = “Category”,values_to = “Value”)Below is code for a reusable RStudio code snippet that generates a fill-in-the-blank code explainer for pivot_longer() whenever you invoke it. This is not R code; it’s snippet code to generate R code:snippet plongerpivot_longer(${1:mydf},cols = ${2:columns to pivot long},names_to = “${3:desired name for category column}”,values_to = “${4:desired name for value column}”)All the items enclosed with ${} are snippet variables. If you don’t know how RStudio code snippets work, you can watch this tutorial video:
You can add the snippets code to your RStudio R code snippets file with the following R command:usethis::edit_rstudio_snippets()That opens the snippets file within RStudio. You can then copy and paste — or type — code into that file. Note that every line under the first line within the snippet and the name of the snippet (plonger) must start with a tab. Sharon Machlis, IDG
Start typing the name of a snippet to select and use it.
To use the snippet, start typing plonger and the snippet name will appear as a choice to select and use. Watch the video embedded at the very top of this article if you want to see the pivot_longer() snippet in action. Added bonus: The snippet already includes quotation marks where they’re needed, so you don’t have to add them.From long to wideTo reshape the other way, use pivot_wider():pivot_wider(mydata, id_cols, # optional vector of columns you do not want affectednames_from, # category column(s) to pivot from long to widevalues_from # value columns(s) that hold data for each category columnnames_sep # optional string separator for category-value columns)For this demo I’ll use the us_rent_income data frame, which has data by US state for median annual income and median monthly rent, plus margins of error for each. GEOID NAME variable estimate moe
<chr> <chr> <chr> <dbl> <dbl>
1 01 Alabama income 24476 136
2 01 Alabama rent 747 3
3 02 Alaska income 32940 508
4 02 Alaska rent 1200 13
5 04 Arizona income 27517 148
6 04 Arizona rent 972 4For a more human-readable version, I’d want income and rent to each have their own columns: income, income margin of error, rent, and rent margin of error. Code for that:rent_income_wide <- pivot_wider(us_rent_income,# id_cols = optional vector of unaffected columns,names_from = c(variable),values_from = c(estimate, moe),names_sep = “_” )The RStudio code snippet below will generate reusable fill-in-the-blank code and explanations for each pivot_wider() argument.snippet pwiderpivot_wider(${1:mydf},# id_cols = ${2:optional vector of unaffected columns},names_from = c(${3:category column(s) to pivot wide}),values_from = c(${4:value column(s) that hold data for each category column}),names_sep = “_” )You can download a text file with both pivot snippets below. Right-click and save the link as a file on your system; don’t copy and paste from the file displayed in a browser. download
Copy and paste this code into your RStudio R code snippets file Sharon Machlis
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