for loop specific file names R

Question

I have a list of identifiers saved as a character variable (uid_car) I have a list of files (file_list) with an identifier as the prefix to file name(eg 1000_*.file)

uid_car<-1000,1002,1004....len(170) file_list<-1000_01_.file,1001_02.file,1003_02.file,1002_01.file,1004_01.file...len(~700)

In the above example I want to loop through the file list and copy the files that have the prefix contained in uid_car. Therefore, only file 1000_01.file, 1002_01.file and 1004_01.file would be copied to a new path.

The following for loop below works until you hit an ith element not contained in uid_car.

I have tried an mapply function which is probably a bit neater but don't have as much experience writing these...any help would be appreciated.

for (i in length_of_file_list) {
  if (startsWith(file_list[i], uid_car[])) {
    file.copy(file_list[i], new_path)
  }
}

Answer 1

If you DO want to do it in a loop, this may do what you're looking for:

uids_to_print <- c("1000", "1001", "1004")
filenames <-c("1000_01.file","1000_02.file","1001_01.file","1001_02.file","1002_01.file","1002_02.file","1003_01.file","1004_01.file")


# Iterate through each filename
for (filename in filenames) {

    # Pull out the characters prior to the first underscore
    filename_uid <- unlist(strsplit(filename, "_"))[1]

    # Cheeck if it's in the list of ones to print
    if(filename_uid %in% uids_to_print) {
        # Put file operation inside this loop

    }
}

for example, executing

for (filename in filenames) {
    filename_uid <- unlist(strsplit(filename, "_"))[1]
    if(filename_uid %in% uids_to_print) {
        print(paste("copy", filename, sep=" "))
    }
}

yields

"copy 1000_01.file"
"copy 1000_02.file"
"copy 1001_01.file"
"copy 1001_02.file"
"copy 1004_01.file"