[R] how to factor in the ID of the imported subtable to R table?

[David Winsemius]

On 5/21/20 9:24 AM, YANJUN CHEN via R-help wrote:
> Dear R community,
>
> I am new to R—did some online tutorials and exercises in R playground. I was wondering if I could seek guidance on the following matter.
>
> I have a set of 403 .csv files. Each.csv file contains the same layouts and distinguished by subject ID and date in the file name. The dataset looks like this:
>
> Sub1-20170305.csv
> Sub2-20180214.csv
> …
> Sub403-20191109.csv


Something along the lines of:

?regex ; ?sub

?read.table

?data.frame

?do.call

?rbind

myfiles <- lapply( list.files(your_path) , # each file name will be 
passed to anonymous function

                            function(nm) data.frame( subID = sub("-.+", 
"",  nm), # remove chars after "-"

date=sub("^.+-(.{8})[.]csv", "\\1", nm), #extract date as capture class

                                             #assuming all files have 
same number of columns with no headers

                                             read.table( 
paste0(your_path, nm) )

big_file <- do.call(rbind, myfiles)

>
> I will use rbind function to combine 403 csv files in a single file (myFile). I will create two new variables (use mutate function) in myFile (subject ID and date). Is there a way to subtract subject ID (shown as “Sub1, 2,,,403”) and date from the name of the csv file and then place them in “subject ID” and “date” in myFile?
>
> Any info on the issue itself or where to look for will be appreciated.


If you search StackOverflow or Rseek with topic terms " stacking 
multiple data files" you should find many worked examples.

> Thanks,
>
> CJ
>
>
>
>
>
>
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Best;

David.

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