How to Collapse Text by Group in a Data Frame Using R


Steven P. Sanderson II, MPH


May 9, 2024


When working with data frames in R, you may often encounter scenarios where you need to collapse or concatenate text values based on groups within your dataset. This could involve combining text from multiple rows into a single row per group, which can be useful for summarizing data or preparing it for further analysis. In this post, we’ll explore how to achieve this task using different methods in R—specifically using base R, the dplyr package, and the data.table package.

Example Data

Let’s start with an example dataset. Suppose we have a data frame df containing information about sales transactions:

# Example data frame
df <- data.frame(
  CustomerID = c(1, 1, 2, 2, 3),
  Product = c("Apple", "Orange", "Banana", "Peach", "Grapes"),
  Quantity = c(2, 3, 1, 2, 1),
  stringsAsFactors = FALSE

# Print the data frame
  CustomerID Product Quantity
1          1   Apple        2
2          1  Orange        3
3          2  Banana        1
4          2   Peach        2
5          3  Grapes        1


Using Base R

In base R, you can use aggregate() to collapse text values by group. Let’s say we want to collapse the Product column by CustomerID:

# Collapse text by CustomerID using base R
collapsed_df <- aggregate(Product ~ CustomerID, data = df, FUN = function(x) paste(x, collapse = ", "))

# Print the result
  CustomerID       Product
1          1 Apple, Orange
2          2 Banana, Peach
3          3        Grapes

Here, we used aggregate() to group the Product column by CustomerID and applied a custom function to concatenate the text values separated by commas.

Using dplyr

The dplyr package provides a concise way to manipulate data frames. We can achieve the same result using dplyr’s group_by() and summarise() functions:

# Load the dplyr package

# Collapse text by CustomerID using dplyr
collapsed_df <- df %>%
  group_by(CustomerID) %>%
  summarise(Product = paste(Product, collapse = ", "))

# Print the result
# A tibble: 3 × 2
  CustomerID Product      
       <dbl> <chr>        
1          1 Apple, Orange
2          2 Banana, Peach
3          3 Grapes       

Using data.table

For larger datasets, the data.table package can offer efficient solutions. Here’s how you can collapse text by group using data.table:

# Load the data.table package

# Convert data.frame to data.table

# Collapse text by CustomerID using data.table
collapsed_df <- df[, .(Product = paste(Product, collapse = ", ")), by = CustomerID]

# Print the result
   CustomerID       Product
        <num>        <char>
1:          1 Apple, Orange
2:          2 Banana, Peach
3:          3        Grapes


In this blog post, we explored different methods to collapse text by group in a data frame using R. Whether you prefer the simplicity of base R, the readability of dplyr, or the efficiency of data.table, each approach allows you to perform this task effectively based on your preference and the size of your dataset.

I encourage you to try these examples with your own datasets and explore further customizations based on your specific needs. Manipulating data in R can be both powerful and intuitive, and mastering these techniques will enhance your data analysis capabilities.

Happy coding!