Adding Sheet Names to DataFrame Output

When working with Excel files, it’s common to have multiple sheets containing related data. These sheets can be labeled based on comparisons made within the dataset. In this article, we’ll explore how to add a sheet name column to your dataframe output using R and the dplyr library.

Background and Context

The provided Stack Overflow question starts by reading an Excel file into an R dataframe named df. The code then retrieves the list of sheet names from the Excel file using the excel_sheets() function. It transforms these sheet names into a list of dataframes, which are then merged back together using the map_dfr() and set_names() functions.

The question also defines a function filter_qval() that filters rows based on a certain q-value threshold. This function is used to filter the dataframe before grouping it by terms (or columns) in the dataframe.

Problem Statement

The user wants to add another column to their output dataframe that includes the sheet name label for each row. This will help them identify which sheet the data originated from.

Solution Overview

To solve this problem, we’ll use the dplyr library to add a new column to the dataframe with the desired sheet names. We’ll leverage the set_names() function to assign meaningful names to these columns and create a clear link between the original dataframe rows and their corresponding Excel sheets.

Step 1: Retrieving Sheet Names

library(dplyr)
library(purrr)

# Read in the Excel file into a dataframe
df <- read_excel("FAB_all_DOWN.xlsx")

# Retrieve the list of sheet names from the Excel file
sheet_names <- excel_sheets()

print(sheet_names)  # Check if the sheet names are retrieved correctly

Step 2: Mapping Sheet Names to Dataframes

# Create a map of dataframes using the sheet names as keys
df_map <- map(sheet_names, ~ read_excel("FAB_all_DOWN.xlsx", .id = .x))

print(df_map)  # Check if the mapping is successful

Step 3: Adding Sheet Names to Dataframe

# Use map_dfr() and set_names() to create a new dataframe with sheet names
df_sheets <- map_dfr(df_map, ~ .x + set_names(.y, ..1))

print(df_sheets)  # Check if the desired output is created

Step 4: Grouping and Filtering

# Define a function to filter rows based on a q-value threshold
filter_qval <- function(df, q_value_rev){
  filter_df <- df[df$q_value_rev < 0.05,]
  return(filter_df)
}

# Filter the dataframe using the filter_qval() function
a <- map_dfr(df_sheets, filter_qval)

print(a)  # Check if the filtered output is correct

Step 5: Adding Sheet Names to Final Output

# Assign meaningful names to the new column containing sheet names
df_sheets$Sheet_Name <- rownames(df_sheets)

# Print the final dataframe with added sheet names
print(df_sheets)

Conclusion

In this article, we demonstrated how to add a column of sheet names to your R dataframe output using dplyr. By leveraging the excel_sheets() and map_dfr() functions, you can create a clear link between original dataframe rows and their corresponding Excel sheets. This addition provides valuable context for analyzing data within different sheets.

Additional Tips and Variations

• Handling Multiple Sheets: If your Excel file has multiple worksheets, ensure that the excel_sheets() function retrieves all sheet names correctly.
• Customizing Column Names: You can modify the column name assigned to the new dataframe using the set_names() function. This allows for clear labeling of each row’s corresponding sheet name.
• Extending Functionality: The filter_qval() function serves as a starting point for more complex filtering operations. Feel free to extend this function or use it as a reference to create your own filtering logic.

By following the steps outlined in this article, you can add useful sheet names to your R dataframe output and unlock deeper insights into your data.

Last modified on 2023-05-13