[R] Rbind-ing a list into one item

[Bert Gunter]

There are at least a couple of "gotchas" that should be noted, however:

1. The files = data.frames can only be rbind-ed (?is this the past tense of
rbind?) if the columns have the same names as well as numbers.

2. The corresponding column classes must be the same for all data.frames.
You may not get errors if this is not true, but silent coercions may end up
changing things from what you expect.

Editorial Comment: I find that both these issues often cause problems in
reading in spreadsheets due to a)typos and inconsistencies in column names
and character columns (especially with spaces and caps)-- which by default
become factors --  and stray characters (e.g., commas or "$" in American
numeric and financial columns). It's very easy for such little problems to
slip into Excel spreadsheets unless the creators are very fastidious, which
most of us aren't. My subjective estimate is that >50% -- and probably
closer to 90% -- of "uncurated" spreadsheets (as opposed to e.g. structured
databases) contain such problems.

Hopefully these issues will not bedevil you.

Cheers,
Bert Gunter
Genentech

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of markleeds at verizon.net
Sent: Wednesday, December 26, 2007 1:37 PM
To: r-help at r-project.org; Kondamani, Arjun (GMI - NY Corporate Bonds)
Subject: Re: [R] Rbind-ing a list into one item

>From: "Kondamani, Arjun (GMI - NY Corporate Bonds)"
<arjun_kondamani at ml.com>
>Date: 2007/12/26 Wed PM 03:23:51 CST
>To: r-help at r-project.org
>Subject: [R] Rbind-ing a list into one item

try do.call(rbind,res)

>Hi,
>
>I am doing the following: 
>
>1. I have a list of files.. Files1=list.files("some
>directory",pattern="some pattern")
>2. I define a list as res=vector("list", length(files1))
>3. I read all the files into this list: res=lapply(files1, read.csv)
>
>I now want to rowbind all the items in the list into one big mass (all
>files have same number of columns). I tried lapply(res, rbind) but that
>did not work. Suggestions?
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