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Reading in multiple files

3 messages · Bliese, Paul D MAJ WRAIR-Wash DC, Fredrik Karlsson, Thomas Lumley

Bliese, Paul D MAJ WRAIR-Wash DC
# 
I apologize if this is a FAQ -- I kind of recall seeing something along
these lines before, but I couldn't find the message when I searched the
archives.

Problem:
1. I have hundreds of small files in a subdirectory ("c:\\temp") and I would
like to combine the files into a single data frame.
2. Individually, it is easy to read each file
3. It is also fairly easy to add new files to the data frame one at a time:
What is tedious about this solution is that we have to change the file name
in step 3 every time.

Is there a way to have R identify all the files in a directory and create
one big data frame?

I'm working in Windows with R 1.6.2.

Thanks

Paul
MAJ Paul Bliese, Ph.D.
Walter Reed Army Institute of Research
Phone: (301) 319-9873
Fax: (301) 319-9484
paul.bliese at na.amedd.army.mil
Fredrik Karlsson
# 
Dear Dr. Bliese,

One way is  to loop over the results of list.files(). Look it up in the
manual.

/Fredrik
On Wed, Apr 09, 2003 at 09:51:38AM -0400, Bliese, Paul D MAJ WRAIR-Wash DC wrote:
Thomas Lumley
#
On Wed, 9 Apr 2003, Bliese, Paul D MAJ WRAIR-Wash DC wrote:

            

      
      
      
    

        
You can get the file list with

   all.the.files <- list.files("C:/temp",full=TRUE)

where full=TRUE asks for absolute file paths, which will be useful if this
isn't your working directory. You could also add pattern="\\.csv$" to
ensure that you only get .csv files.


Then you could read them all in

  all.the.data <- lapply( all.the.files,  read.csv, header=TRUE)

and then rbind them into a data frame

  DATA <- do.call("rbind", all.the.data)

In one line this would be

DATA <- do.call("rbind", lapply( list.files("C:/temp",full=TRUE),
		read.csv, header=TRUE))


It should be faster to use do.call("rbind",) rather than a loop, but I
don't know if it actually is.


	-thomas