[R] Wriritng to a CSV file

Uwe Ligges ligges at statistik.tu-dortmund.de
Wed Feb 8 20:38:17 CET 2012

I (and you as well) should have seen that before: use write.table in 
order to append. The reason for that is given in ?write.table / ?write.csv:

      ‘write.csv’ and ‘write.csv2’ provide convenience wrappers for
      writing CSV files.  They set ‘sep’ and ‘dec’ (see below), ‘qmethod
      = "double"’, and ‘col.names’ to ‘NA’ if ‘row.names = TRUE’ (the
      default) and to ‘TRUE’ otherwise.

      ‘write.csv’ uses ‘"."’ for the decimal point and a comma for the

      ‘write.csv2’ uses a comma for the decimal point and a semicolon
      for the separator, the Excel convention for CSV files in some
      Western European locales.

      These wrappers are deliberately inflexible: they are designed to
      ensure that the correct conventions are used to write a valid
      file.  Attempts to change ‘append’, ‘col.names’, ‘sep’, ‘dec’ or
      ‘qmethod’ are ignored, with a warning.

Uwe Ligges

On 08.02.2012 20:29, Ron Michael wrote:
> Okay, so I understood that appending can only happen row-wise. Therefore I tried with following code:
>> write.csv(matrix(1:5, 1), "dat.csv")
>> write.csv(matrix(1:5, 1), "dat.csv", append = TRUE)
> Warning message:
> In write.csv(matrix(1:5, 1), "dat.csv", append = TRUE) :
>    attempt to set 'append' ignored
> It is destroying my previous file. Where I have done wrong?
> Thanks,
> ----- Original Message -----
> From: Uwe Ligges<ligges at statistik.tu-dortmund.de>
> To: Ron Michael<ron_michael70 at yahoo.com>
> Cc: "r-help at r-project.org"<r-help at r-project.org>
> Sent: Thursday, 9 February 2012 1:07 AM
> Subject: Re: [R] Wriritng to a CSV file
> On 08.02.2012 20:14, Ron Michael wrote:
>> Dear all, let say I want to write a vector to a CSV file. So I can have following syntax:
>> write.csv(rnorm(10), "dat.csv")
>> Now I want to add one more column into that existing file. If I use the same code then existing file will be destroyed. Is there any functionality to add without destroying the existing file? I have tries with 'append = TRUE' however it is not working!
>> Any suggestion will be highly appreciated.
> Since these text files are written line by line, you cannot add a column
> afterwards, you can just append rows.
> Hence read the first column and write a two column data.frame afterwards.
> Uwe Ligges
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