R help - Apr 2012 - How to insert filename as column in a file

Hi,

I am relatively new to R. Have scourged the help files and the www but
havent been able to get a solution.

I have around 250 csv files, one file for each date. They have columns of
all types, numeric, string etc. The name of each file is the date in the
form of 'yyyymmdd'. There is no column within the file which helps me
identify the date on which the file was generated, only the filename has
that info.

I am selecting some data (using read.csv.sql) from each file and creating a
dataset for each day. Ultimately I will combine all the datasets. I can
accomplish the select and combine part, but after combining I wont have a
record as to the date corresponding to the data.

Hence I want to insert the filename as a column in the respective file to
help me in identifying to what date each data row belongs to.

Sorry for the long mail, but wanted to make myself clear. Any help would be
greatly appreciated.

Thanks in advance,
Shivam

	[[alternative HTML version deleted]]

This might do it for you:


for (i in fileNames){
    input <- read.table(i, .....)
   # you might want to use regular expressions to extract just the date.
    input$fileName <- i
    write.table(i, ....)
}

On Mon, Apr 23, 2012 at 12:29 PM, Shivam <shivamsingh at gmail.com>
wrote:
> Hi,
>
> I am relatively new to R. Have scourged the help files and the www but
> havent been able to get a solution.
>
> I have around 250 csv files, one file for each date. They have columns of
> all types, numeric, string etc. The name of each file is the date in the
> form of 'yyyymmdd'. There is no column within the file which helps
me
> identify the date on which the file was generated, only the filename has
> that info.
>
> I am selecting some data (using read.csv.sql) from each file and creating a
> dataset for each day. Ultimately I will combine all the datasets. I can
> accomplish the select and combine part, but after combining I wont have a
> record as to the date corresponding to the data.
>
> Hence I want to insert the filename as a column in the respective file to
> help me in identifying to what date each data row belongs to.
>
> Sorry for the long mail, but wanted to make myself clear. Any help would be
> greatly appreciated.
>
> Thanks in advance,
> Shivam
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.

This little example might help.
> foo <- data.frame(a=1:10, b=letters[1:0])
> foo
    a b
1   1 a
2   2 a
3   3 a
4   4 a
5   5 a
6   6 a
7   7 a
8   8 a
9   9 a
10 10 a
> foo$date <- '20120423'
> foo
    a b     date
1   1 a 20120423
2   2 a 20120423
3   3 a 20120423
4   4 a 20120423
5   5 a 20120423
6   6 a 20120423
7   7 a 20120423
8   8 a 20120423
9   9 a 20120423
10 10 a 20120423


In other words, immediately after reading the data into a data frame, add
a date column as in the example. You'll have to extract the date from the
filename, of course.

-Don


-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062





On 4/23/12 9:29 AM, "Shivam" <shivamsingh at gmail.com> wrote:
>Hi,
>
>I am relatively new to R. Have scourged the help files and the www but
>havent been able to get a solution.
>
>I have around 250 csv files, one file for each date. They have columns of
>all types, numeric, string etc. The name of each file is the date in the
>form of 'yyyymmdd'. There is no column within the file which helps
me
>identify the date on which the file was generated, only the filename has
>that info.
>
>I am selecting some data (using read.csv.sql) from each file and creating
>a
>dataset for each day. Ultimately I will combine all the datasets. I can
>accomplish the select and combine part, but after combining I wont have a
>record as to the date corresponding to the data.
>
>Hence I want to insert the filename as a column in the respective file to
>help me in identifying to what date each data row belongs to.
>
>Sorry for the long mail, but wanted to make myself clear. Any help would
>be
>greatly appreciated.
>
>Thanks in advance,
>Shivam
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
>R-help at r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.