[R] sequencially merge multiple files in a folder

Greg Snow Greg.Snow at imail.org
Tue Nov 18 17:37:47 CET 2008

If you know how to merge 2 of the files together, then you can use the Reduce function to do the merging of multiple files.

You could use lapply to read all of the files into a list, then Reduce to merge them together, then output the result to a new file if a file is really what you want.

Another approach may be to use one of the database packages and an sql query to merge everything together.

Hope this helps,

Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Ping-Hsun Hsieh
> Sent: Monday, November 17, 2008 10:38 PM
> To: r-help at r-project.org
> Subject: [R] sequencially merge multiple files in a folder
> Dear all,
> If the question is too easy, please forgive me since I am only few
> weeks old in R.
> I have worked on this question a  few days and still cannot figure it
> out.
> Here I have a folder with more than 50 tab-delimited files. Each file
> has a few hundreds of  thousands rows/subjects, and the number of
> columns/variables of each file varies.The 1st row consists of all the
> variable names.
> Now I would like to merge all the files into one tab-delimited file by
> a common column named "Ident"
> Is there any good way to sequencially merge all of them together?
> Here when I say  "sequencially" I mean merging file_1  and file_2
> first and then merge the resulting data frame and file_3, and keep
> going on and on till all files are merged.
> If it is too complicated to do, merging all files together without the
> specified order is also an acceptable alternative.
> Here I am using R version 2.7.2 (2008-08-25) and x86_64-unknown-linux-
> gnu.
> Thank you for any advice and help!
> PingHsun

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