[R] sequencially merge multiple files in a folder

[Greg Snow]

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
801.408.8111


> -----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