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 <macque...@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" <shivamsi...@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@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.
>
>
--
*Victoria Concordia Crescit*
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