Question

I have a data set that looks like:

Files          Batch
filepath1.txt   One
filepath2.txt   One
filepath3.txt   One
filepath4.txt   One
filepath5.txt   two
filepath6.txt   two
filepath7.txt   two
filepath8.txt   two

I want to loop over the full data set (that has a dozen “Batch” categories) by creating groups of “Files” that is based on what “Batch” they’re in, in a new variable called “batch”

i.e.

batch[1] 
filepath1.txt
filepath2.txt
filepath3.txt
filepath4.txt

batch[2]
filepath5.txt
filepath6.txt
filepath7.txt
filepath8.txt

How do I do this for all my Batch groups in the full data-set?

Answer 1

The split function seems to be what you’re looking for.

> dat <- data.frame(File = paste0("file", 1:10, ".txt"), Batch = rep(c("one", "two"), each = 5))
> dat
         File Batch
1   file1.txt   one
2   file2.txt   one
3   file3.txt   one
4   file4.txt   one
5   file5.txt   one
6   file6.txt   two
7   file7.txt   two
8   file8.txt   two
9   file9.txt   two
10 file10.txt   two
> split(dat, dat$Batch)
$one
       File Batch
1 file1.txt   one
2 file2.txt   one
3 file3.txt   one
4 file4.txt   one
5 file5.txt   one

$two
         File Batch
6   file6.txt   two
7   file7.txt   two
8   file8.txt   two
9   file9.txt   two
10 file10.txt   two