Read one worksheet from multiple excel files using purrr and readxl and add field

Question

Suppose I have two excel files named packs .xlsx and each contains multiple sheets. I want to iteratively create a dataframe using only 1 sheet from each file, each named "summary". How can I go about this using Purrr and readxl while also adding a field which contains the filename?

I'm successful when I save the sheets as CSVs using the following code:

filenames <- list.files(pattern="packs*.*csv")
dat <- map_dfr(filenames, read_xlsx, sheet = "summary") %>% glimpse()

How would I go about adding a field to show which file a given row came from? Thanks for any insight that can be offered!

Answer 1

Supposing the two packs.xlsx files are in different subfolders:

library(readxl)

filenames <- list.files(pattern = "packs.xlsx", recursive = TRUE)
df <- lapply(filenames, function(fn) {
  # get the sheet detail 
  xl <- read_excel(fn, sheet = "summary")    
  
  # add the filename as a field
  xl$filename <- fn            

  # function return                     
  xl
})

# if both summary sheets have the same format, you can combine them into one 
fin <- do.call(rbind, df)