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How do I read a variable number of files and then concatenate the data in R?

I would like to create a function. Let's say I have files file1.csv, file2.csv, file3.csv, ..., file100.csv. I only want to read some of them every time I call the function giving an integer vector id like id = 1:10, then I will read file1.csv, ..., file10.csv.

After reading these csv files, I would like them to combine them into one variable. All csv files have the same column structure.

My code is below:

  namelist <- list.files() 
  for (i in id) { 
    assign(paste0( "file", i ), read.csv(namelist[i], header=T))
  }

As you can see, after reading the entire data matrix, I stuck with a combination of them since they all have different variable names.

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3 answers


You must read in each file as a list item. Then you can combine them like this:

namelist <- list.files()
df <- vector("list", length = length(id))
for (i in id) {
    df[[i]] <- read.csv(namelist[i], header = TRUE)
}
df <- do.call("rbind", df)


Or more succinctly:

df <- do.call(rbind, lapply(list.files(), read.csv))
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I do this, which is greater than R, as without the for loop:



## assuming you have a folder full of .csv to merge
filenames <- list.files()

all_files <- Reduce(rbind, lapply(filenames, read.csv))
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If I understand correctly what you want to do, this is all you need:

namelist <- list.files() 
singlevar = c()
for (i in id) { 
  singlevar = rbind(singlevar, read.csv(namelist[i], header=T))
}

Since at the end you want one single object to contain all the partial information from the individual files rbind

, as you go.

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