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]]

foo <- data.frame(a=1:10, b=letters[1:0])
foo

foo$date <- '20120423'
foo

Reposting in hope of a reply.

On Tue, Apr 24, 2012 at 1:12 AM, Shivam <shivamsingh at gmail.com> wrote:

Thanks for the quick response. It works for an individual dataframe,

but I

have many dataframes. This is the code so far

fnames = list.files(path = getwd())
for (i in 1:length(fnames)){
assign(paste("file",i,sep=""),read.csv.sql(fnames[i], sql = "select *

from

file where V3 == 'XXX' and V5=='YYY'",header = FALSE, sep= '|', eol =

"\n"))

}

This generates dataframes named as as file1,file2,...,file250. Is

there a

way to do something like below within the same loop?

file1$date = substr(fnames[1],1,8))
file2$date = substr(fnames[2],1,8))
.
.
file250$date = substr(fnames[250],1,8))

assign(paste("file",i,sep="")$date doesnt work.

Any help?





On Tue, Apr 24, 2012 at 12:01 AM, MacQueen, Don

<macqueen1 at llnl.gov>wrote:

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]]

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*Victoria Concordia Crescit*

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*Victoria Concordia Crescit*

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