Can't name loaded files - R

Question

So I have a folder with bunch of csv, I set the wd to that folder and extracted the files names:

data_dir <- "~/Desktop/All Waves Data/csv"  
setwd(data_dir)  
vecFiles <- list.files(data_dir)

all good, now the problem comes when I try to load all of the files using a loop on vecFiles:

for(fl in vecFiles) { 
fl <- read.csv(vecFiles[i], header = T, fill = T) 
}

The loop treats 'fl' as a plain string when it comes to the naming, resulting only saving the last file under 'fl' (by overwriting the previous one at each time).

I was trying to figure out why this happens but failed.
Any explanation?

Edit: Trying to achieve the following: assume you have a folder with data1.csv, data2.csv ... datan.csv, I want to load them into separate data frames named data1, data2 ..... datan

Answer 1

You want to read in all csv file from your working directory and have the locations of those files saved in vecFiles.

Why your attempt doesn't work

What you are currently doing doesn't work, because you are overwriting the object fn with the newly loaded csv file in every iteration. After all iterations have been run through, you are left with only the last overwritten fn object.

Another example to clarify why fn only contains the value of the last csv-file: If you declare fn <- "abc" in line1, and in line2 you say fn <- "def" (i.e. you overwrite fn from line1) you will obviously have the value "def" saved in fn after line2, right?

fn <- "abc"
fn <- "def"
fn
#[1] "def"

Solutions

There are two prominent ways to solve this: 1) stick with a slightly altered for-loop. 2) Use sapply().

1) The altered for loop: Create an empty list called fn, and assign the loaded csv files to the i-th element of that list in every iteration:

fn <- list()
for(i in seq_along(vecFiles)){
  fn[[i]] <- read.csv(vecFiles[i], header=T, fill=T)
}
names(fn) <- vecFiles

2) Use sapply(): sapply() is a function that R-users like to use instead of for-loops.

fn <- sapply(vecFiles, read.csv, header=T, fill=T)
names(fn) <- vecFiles

Note that you can also use lapply() instead of sapply(). The only difference is that lapply() gives you a list as output

Answer 2

You're not declaring anything new when you load the file. Each time you load, it loads into fl, because of that you would only see the last file in vecFiles.

Couple of potential solutions.

First lapply:

fl <- lapply(vecFiles, function(x) read.csv(x, header=T, fill=t) )
names(fl) <- vecFiles

This will create a list of elements within fl.

Second 'rbind':

Under the assumption your data has all the same columns:

fl <- read.csv(vecFiles[1], header=T, fill=t)

for(i in vecFiles[2:length(vecFiles)]){
fl <- rbind(fl, read.csv(vecFiles[i], header=T, fill=t) )
}

Hopefully that is helpful!