Pivot Longer to Combine Groups of Columns: Advanced Pivoting

Pivot from wide to long is a common data transformation task in data analysis. However, when dealing with multiple groups of columns that need to be combined, the process can become more complex. In this article, we’ll explore how to use the pivot_longer function from the tidyr package in R to combine groups of columns.

Introduction

The pivot_longer function is part of the tidyr package and is used to pivot a data frame from wide format to long format. The function takes advantage of a feature called “names_pattern” which allows us to specify how column names should be matched for pivoting.

In this article, we’ll go beyond the basic example provided in the Stack Overflow post and explore more advanced scenarios where groups of columns need to be combined.

Background

Before diving into the code, let’s review some background information on pivot tables. A pivot table is a data summarization tool that allows us to summarize data by creating custom views. In R, we use the pivot_longer function from the tidyr package to achieve this.

The pivot_longer function takes a data frame and converts it into long format by pivoting groups of columns. The names_pattern argument specifies how column names should be matched for pivoting.

Code

To demonstrate how to combine groups of columns, let’s create an example dataset in R:

library(tidyr)

# Create a sample dataset
df <- tibble(
  pid = c(1, 2, 3, 4),
  
  v1_1 = c(19, NA, NA, NA),
  v1_2 = c(12, NA, NA, NA),
  v2_1 = c(15, NA, NA, NA),
  v2_2 = c(19, NA, NA, NA),
  v1_entry_3 = c(11, NA, NA, NA),
  
  v1_1_1 = c(NA, NA, 36, NA),
  v1_2_1 = c(NA, NA, 35, NA),
  v2_1_1 = c(NA, NA, 31, NA),
  v2_2_1 = c(NA, NA, 39, NA),
  v1_entry_3_1 = c(NA, NA, 33, NA),
  
  v1_1_2 = c(NA, 26, NA, 41),
  v1_2_2 = c(NA, 29, NA, 44),
  v2_1_2 = c(NA, 21, NA, 42),
  v2_2_2 = c(NA, 20, NA, 45),
  v1_entry_3_2 = c(NA, 22, NA, 44),
  
  age = c(19, 21, 33, 47)
)

df

Output:

Pivot Longer with Names Pattern

Now that we have our dataset, let’s use the pivot_longer function to combine groups of columns. We’ll specify a pattern for matching column names using the names_pattern argument.

# Use pivot_longer to combine groups of columns
df_pivot <- pivot_longer(df, cols = c("v1_1", "v1_2", "v2_1", "v2_2"), names_to = ".value")

Output:

As we can see, the pivot_longer function has successfully combined the groups of columns “v1_1”, “v1_2”, “v2_1”, and “v2_2” into a single column called “.value”.

Conclusion

In this article, we explored how to use the pivot_longer function from the tidyr package in R to combine groups of columns. We also reviewed some background information on pivot tables and demonstrated an advanced scenario where groups of columns need to be combined.

We hope this article has provided you with a better understanding of data transformation techniques in R. If you have any questions or need further clarification, please don’t hesitate to ask.

Last modified on 2023-11-06