Saving deeply nested files to specific directories with specific filenames

问题

Given a 3 level nested list:

mylist <- list("1000"=list("cars"=list("fast"=mtcars[1:10,], "slow"=mtcars[11:15,]), "flower"=iris), "2000"=list("tooth"=ToothGrowth, "air"=airquality, "cars"=list("cruiser"=mtcars[5:12,], "fast"=mtcars[1:3,], "mild"=mtcars[9:18,])))

(ie: mylist$1000$cars$fast, where fast is a dataframe, and cars and 1000 are nested lists in mylist)

I'd like to save each innermost dataframe, (ie: fast) as a .csv with the df name as it's file name, ie: fast.csv, and I want the file to be saved in a directory that is named after the second level of list, ie: ~/1000/fast.csv.

Each directory already exists, so I do not need to create a new 1000 and 2000 directory.

My instinct is to do a nested lapply or lapply/mapply combination...but keeping track of the different levels and their names is challenging me. I know that purrr has the iwalk function, but I'm not sure how to use it within deeply nested list.

My current attempt fails.

lapply(mylist, function(d){
  lapply(names(mylist), function(id){
    lapply(names(d$cars), function(s){
    lapply(d$cars, function(a){
        write.csv(a, paste0(outdir, id, "/", s, ".csv"))})})})})

The output results in a single file being saved under multiple names into all the directories. ie: ~/1000/cruiser.csv, ~/1000/fast.csv, ~/1000/mild.csv, ~/2000/cruiser.csv, ~/2000/fast.csv, ~/2000/mild.csv ... where all the files are actually just a csv of mylist$2000$cars$mild

回答1:

Assuming the sub-folders are within the working directory:

purrr::iwalk(mylist, function(el, folder){
  purrr::walk(el,
              function(sub_el, folder){
                if(class(sub_el) == "list"){
                  purrr::iwalk(sub_el,
                               function(dat, dat_name, folder){
                                 write.csv(dat,
                                           # below line specifies file path of new file
                                           paste0(folder, "/", dat_name, ".csv"))
                               },
                               folder = folder)
                }
              },
              folder = folder)
})

来源：https://stackoverflow.com/questions/52819642/saving-deeply-nested-files-to-specific-directories-with-specific-filenames

标签

lapply

purrr

mapply