R - Dynamic reference to files for read csv - r

Question

I would like to make a script that reads data from the correct folder. I have several lines in my code refering to the foldername, therefore I would like to make this dynamic. Is it possible to make the reference to a folder name dynamic? See below what I would like to do
# Clarifies the name of the folder, afterwards "Foldername" will be used as reference
FolderA <- Foldername
# Read csv to import the data from the selected location
data1 <- read.csv(file="c:/R/Foldername/datafile1.csv", header=TRUE, sep=",")
data2 <- read.csv(file="c:/R/Foldername/datafile2.csv", header=TRUE, sep=",")
I am trying to get the same result as what I would get with this code:
data1 <- read.csv(file="c:/R/FolderA/datafile1.csv", header=TRUE, sep=",")
data2 <- read.csv(file="c:/R/FolderA/datafile2.csv", header=TRUE, sep=",")
Can somebody please clarify how it would be possible to make this dynamic?

Answer 1

You could use paste0 for this:
FolderA <- "Foldername"
paste0("c:/R/", FolderA, "/datafile1.csv")
#[1] "c:/R/Foldername/datafile1.csv"
So in your case:
data1 <- read.csv(file=paste0("c:/R/", FolderA, "/datafile1.csv"), header=TRUE, sep=",")

Answer 2

A slight generalization of #LyzandeR's answer,
make_files <- function(directory, filenames) {
sprintf("C:/R/%s/%s", directory, filenames)
}
##
Files <- sprintf("file%i.csv", 1:3)
##
make_files("FolderA", Files)
#[1] "C:/R/FolderA/file1.csv" "C:/R/FolderA/file2.csv" "C:/R/FolderA/file3.csv"

Answer 3

you could also try the following method. The loop will create a list with output file, but if your files all have the same column names you could just rbind them together (method 2). This method will allow you to specify your folder, then use the list.files function to extract all files with extension ".csv". This way if you have many csv files in a folder you won't have to write them all out individually.
# Specify working directory or location of files:
FolderA = "c:/R/Foldername"
# identify all files with specific extension:
files = list.files(FolderA,pattern="*.csv")
Method 1 - Separate by lists
data = NULL
for(i in 1:length(files)){
data[[i]] = read.csv(files[i],header=F,stringsAsFactors=F)
}
Method 2 - single dataframe
data = NULL
for(i in 1:length(files)){
df = read.csv(files[i],header=F,stringsAsFactors=F)
data = rbind(data,df)
}