How do I rename files using R?

Question

I have over 700 files in one folder named as: files from number 1 to number9 are named for the first month:

water_200101_01.img  
water_200101_09.img  

files from number 10 to number30 are named:

water_200101_10.img
water_200101_30.img

And so on for the second month: files from number 1 to number9 are named:

water_200102_01.img  
water_200102_09.img  

files from number 10 to number30 are named:

water_200102_10.img
water_200102_30.img 

How can I rename them without making any changes to the files. just change the nams, for example

water_1
water_2
...till...
water_700

Answer 1

file.rename will rename files, and it can take a vector of both from and to names.

So something like:

file.rename(list.files(pattern="water_*.img"), paste0("water_", 1:700))

might work.

If care about the order specifically, you could either sort the list of files that currently exist, or if they follow a particular pattern, just create the vector of filenames directly (although I note that 700 is not a multiple of 30).

I will set aside the question, "why would you want to?" since you seem to be throwing away information in the filename, but presumably that information is contained elsewhere as well.

Answer 2

I wrote this for myself. It is fast, allows regex in find and replace, and supports "trial runs".

If you are are on a mac, it can use applescript to pick out the current folder in the Finder as a target folder.

umxRenameFile <- function(baseFolder = "Finder", findStr = NA, replaceStr = NA, listPattern = NA, test = T, overwrite = F) {
    # uppercase = u$1
    if(baseFolder == "Finder"){
        baseFolder = system(intern = T, "osascript -e 'tell application \"Finder\" to get the POSIX path of (target of front window as alias)'")
        message("Using front-most Finder window:", baseFolder)
    } else if(baseFolder == "") {
        baseFolder = paste(dirname(file.choose(new = FALSE)), "/", sep = "") ## choose a directory
        message("Using selected folder:", baseFolder)
    }
    if(is.na(listPattern)){
        listPattern = findStr
    }
    a = list.files(baseFolder, pattern = listPattern)
    message("found ", length(a), " possible files")
    changed = 0
    for (fn in a) {
        findB = grepl(pattern = findStr, fn) # returns 1 if found
        if(findB){
            fnew = gsub(findStr, replace = replaceStr, fn) # replace all instances
            if(test){
                message("would change ", fn, " to ", fnew)  
            } else {
                if((!overwrite) & file.exists(paste(baseFolder, fnew, sep = ""))){
                    message("renaming ", fn, "to", fnew, "failed as already exists. To overwrite set T")
                } else {
                    file.rename(paste(baseFolder, fn, sep = ""), paste(baseFolder, fnew, sep = ""))
                    changed = changed + 1;
                }
            }
        }else{
            if(test){
                # message(paste("bad file",fn))
            }
        }
    }
    message("changed ", changed)
}