Question

I have several .csv files with similar filenames except a numeric month (i.e. 03_data.csv, 04_data.csv, 05_data.csv, etc.) that I’d like to read into R.

I have two questions:

• Is there a function in R similar to
  MATLAB’s varname and assignin that
  will let me create/declare a variable name
  within a function or loop that will allow me to
  read the respective .csv file – i.e.
  03_data.csv into 03_data data.frame,
  etc.? I want to write a quick loop to
  do this because the filenames are
  similar.
• As an alternative, is it better to
  create one dataframe with the first
  file and then append the rest using a
  for loop? How would I do that?

Answer 1

You could look at this related question. You can create the file names easily with a paste command:

file.names <- paste(sprintf("%02d",1:10), "_data.csv", sep="")

Once you have your file names (whether by creating them or by reading them from the directory as in the other question), you can import them quickly with an lapply:

import.list <- lapply(file.names, read.csv)

Lastly, to combine the list into one dataframe, the easiest approach is to use the reshape function below:

library(reshape)
data <- merge_recurse(import.list)