Applying R read_fwf to a list of files

Question

I want to read a directory of fixed width files into a single dataframe, and have tried using read_fwf from readr to do this using the following code:

library(plyr)
library(tidyverse)

file_list <- dir("./Data", full.names = TRUE)

col_widths <- rep.int(5, 4160)
data_import <- ldply(file_list, function(x) read_fwf(fwf_widths(col_widths), skip = 2))

This returns the error:

 Error: `file` must be a string, raw vector or a connection. 

If I do read_fwf(file_list[[1]], fwf_widths(col_widths), skip = 2) then this does successfully import the data from the single file. What is the error that stops read_fwf from being applied to each element of file_list? Am I misunderstanding what ldply does?

Many thanks

Answer 1

You need to pass the data as first argument in read_fwf. Try :

data_import <- ldply(file_list, function(x) 
                      read_fwf(x, fwf_widths(col_widths), skip = 2))

plyr has been retired so you might be interested in these alternate solutions :

#Option 1
data_import <- purrr::map_df(file_list, function(x) 
                    read_fwf(x, fwf_widths(col_widths), skip = 2))

#Option 2
data_import <- do.call(rbind, lapply(file_list, function(x) 
                   read_fwf(x, fwf_widths(col_widths), skip = 2)))