Suggestions for vectorizing/double loop

Well, your second post is rather confusing too, as is your not reproducible code.

If I understand correctly, you just want to change names of files in a directory according to some rules, which you did not clerly specify.

First I am not sure if R is the best tool for it. Nevertheless, you do not change a contents of any file, just change the name.

I found this with simple answer questioning internet.
http://stackoverflow.com/questions/10758965/how-do-i-rename-files-using-r

Is this what you want?

Here is another possibility
https://www.r-bloggers.com/operating-on-files-with-r-copy-and-rename/

Anyway the concept I would use is.

#read old names

old_names <- list.files(old_path)

#setting new names (you did not explain how do you want to do this)
new_names <- some vector of new names

If order of names is correct
file.rename(old_names, new_names)

othervise it would be needed correctly order both vectors before file.rename.

The crucial information is how do you want set the new names vector. You shold specify it by reproducible way if you want more precise answer.

Copying files is in this case best done by OS itself.

Cheers
Petr

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Luanna
Dixson
Sent: Monday, January 23, 2017 6:39 PM
To: r-help at r-project.org
Subject: Re: [R] Suggestions for vectorizing/double loop

Hi all,

Thanks very much for your help! You are correct in thinking the list is the
same as before, actually, my question was more about how to do the next
steps, where I needed to match the filenames of the files in my directory
with old (i.e current) and new file name prefixes in my list. For each match I
then wanted to rename the original file using the corresponding new
filename prefix from the list.

Sorry for being a bit confusing, I didn't post my first attempt to do this at first
as my code just didn't work at all, but I have had another go using a matrix
instead and I think this does the job.

old_path="./old/"
new_path="./new/"

old_names <- list.files(old_path)
head(old_names)

oldnames=c('1002', '1003')
newnames=c('1002_new', '1003_new')
mapping=cbind(oldnames,newnames)
head(mapping)

for (i in old_names){
    temp <- unlist(strsplit(i, "[.]"))[1]
    n <- which(is.element(mapping,temp))
    if(length(n)>0) {
        #copy the file to the new folder
        #re name it and the name is paste(mapping[n,2], '.xls', sep="")
        print(paste(mapping[n,2], '.xls', sep=""))
        newnames <- paste(mapping[n,2], '.xls', sep="")
        file.copy(from = paste(old_path, i, sep=""),
                  to = paste(new_path, newnames))
    }
}


On 23 January 2017 at 13:28, Luanna Dixson
<justanotherdigression at gmail.com>
wrote:

I need to rename a bunch of files, by searching for string matches in
a list. Each list element containings a character with the old
filename that I want to match to, and the new file name that I want to

rename by.

For instance, here filename '1001.xls' should match to
list[[1]]$oldname and I want to rename it to 'newa.xls' from

list[[1]]$newname.

The actual new file names I have will feature a random alphanumeric
number and the list will have a length of ~600.


# files I want to rename

files with old file name =c('1001.xls', '1002.xls')

# list with old file names and new file names

oldnames=c('1001', '1002', '1003')

newnames=c('newa', 'newb', 'newc')

df=data.frame(oldnames,newnames)

list <- split(df, rownames(df))


# turn list elements in character

for(i in 1:length(list)) list[[i]]$oldnames=as.
character(list[[i]]$oldnames)

for(i in 1:length(list)) list[[i]]$newnames=as.
character(list[[i]]$newnames)


I heard that it would be better to vectorize this than trying to do a
double loop so if someone could give me a hint about how to do this I
would be very grateful!

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