How to create a function read multiple data frames as a list in R

Question

I'm having trouble reading several data files at once. If I want someone to plug in their file directory and have the function read all the files in it, how would I go about it?

I have a folder with 15 files that need to be read. So doing this manually was fine until I decided to use the lapply function - I don't want to use a loop. Here was my code:

files <- list.files(path = "/User/Zoe/Documents etc.....", pattern = ".csv")
all_df <- lapply(files, read.table(file, header = TRUE, fill = TRUE, skip = 1)).

An error shows up saying : 'file' must be a character string or connection. I'm guessing when I use the parameter "files" in lapply it is not the correct type of variable?

Then lastly, how would I be able to create a function of the above (assuming it worked)? I'd go about it like this:

read_all_data <- function(folder_name, dir) {
 files <- list.files(dir, pattern = ".csv")
 all_df <- lapply(files, read.table(file, header = TRUE, fill = TRUE, skip = 1)). 
}

Thanks for the help! The actual reading all files is more important to me than the function!

Ronak Shah · Accepted Answer · 2020-12-04 04:50:23Z

1

You have slight syntax error. Either use this :

read_all_data <- function(dir) {
  files <- list.files(dir, pattern = ".csv", full.names = TRUE)
  all_df <- lapply(files, read.table, header = TRUE, fill = TRUE, skip = 1)
  return(all_df)
}

Or with an anonymous function.

read_all_data <- function(dir) {
  files <- list.files(dir, pattern = ".csv", full.names = TRUE)
  all_df <- lapply(files, function(x) 
                   read.table(x, header = TRUE, fill = TRUE, skip = 1))
  return(all_df)
}

edited Dec 4, 2020 at 4:50

answered Dec 4, 2020 at 2:51

Ronak Shah

391k20 gold badges173 silver badges237 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user135688 Over a year ago

Thank-you, the syntax compiled however when I use the function and plug in read_all_data("my path etc ") is just returns : list().

Ronak Shah Over a year ago

Can you share the exact command that you ran?

Collectives™ on Stack Overflow

How to create a function read multiple data frames as a list in R

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related