CODEWITHSUNDEEP
r
Nathalie
Nathalie

Reputation: 1238

Insert a column with file name

Having this code it is possible to read multiple csv from a file path

setwd("C:/Users/Nathalie/mycsvs")
files <- list.files(path = "C:/Users/Nathalie/mycsvs",pattern = ".csv")
temp <- lapply(files, fread, sep=",")

How is it possible to add a column to the dataframe which will have the file name each row came from?

Upvotes: 1

Views: 3245

Answers (1)

Ronak Shah
Ronak Shah

Reputation: 389325

We can use Map and create a new column with cbind to show filename for each file.

Map(cbind, lapply(files, data.table::fread, sep=","), filename = files)

We can also use functions from purrr package to do the same.

library(purrr)
map2(map(files, data.table::fread, sep=","), files, cbind)

To use lapply, we can loop over the index of filenames instead and use transform to add new column with name of the file. 

lapply(seq_along(files), function(x) transform(read.csv(files[x]), file = files[x]))

Upvotes: 4

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