Exporting List Structure to Folder Structure

Question

I have a list 'list_export' with two sub-lists 'list_plots' and 'list_tables', containing ggplots and data frames respectively.

list_plots <- list(plot1, plot2, plot3)
list_tables <- list(table1, table2, table3)
list_export <- list(list_plots, list_tables)

I would like to export the tree structure of the list into a folder structure with the correct data type, such as:

list_export/list_plots/plots[1-3].png
list_export/list_tables/tables[1-3].csv

Is there any way to export the structure of the list directly to folders? It would like to apply the solutions to n-levels, not just 2.

score 1 · Accepted Answer · edited May 23 '17 at 12:17

There's nothing built in that would do anything like this. You could create a function that could help. Maybe something like this

savers <- list(
    "ggplot" = function(pp, base) ggsave(filename=paste0(base,".png"), plot=pp),
    "data.frame" = function(dd, base) write.table(dd, file=paste0(base,".txt"))
)

save_list <- function(x, prefix=deparse(substitute(x)), savers=savers) {
  ids = as.character(if(!is.null(names(x))) {names(x)} else {seq_along(x)})
  ids[nchar(ids)<1] <- as.character(seq_along(x)[nchar(ids)<1])
  ret <- Map(function(x, id) {
     found <- FALSE
     for(type in names(savers)) {
       if(inherits(x, type)) {
           found <- TRUE
           ret <- savers[[type]](x, file.path(prefix, id))
           return(ret)
       }
     }
     if (!found) {
       if (class(x)=="list") {
          save_list(x, file.path(prefix, id), savers=savers)
       } else {
          stop(paste("unable to save object of type:", class(x)))
       }
     }
  }, x, ids)
  invisible(ret)
}

Here I create a list of savers that look at the different object types and write them out to disc. Then with a sample list

plot_list <- Map(function(x) ggplot(mtcars) + geom_point(aes(cyl, disp)) + ggtitle(x), paste("plot", 1:3))
data_list <- replicate(4, data.frame(x=runif(10), y=rnorm(10)), simplify=FALSE)
x <- list(plot_list=plot_list, data_list=data_list)

I can write them out with

save_list(x)

Note that you really need a named list in order to determine file names later. Here I explicitly name the elements of x but if they are not present, simple indexing will be used. You can also swap out the saving functions to see what would be written by just printing the value to screen.

noop <- list(
    "ggplot" = function(pp, fn) print(paste(paste0(fn,".png"),"(plot)")),
    "data.frame" = function(dd, fn) print(paste(paste0(fn,".txt"), "(df)"))
)
save_list(x, savers=noop)
# [1] "x/plot_list/plot 1.png (plot)"
# [1] "x/plot_list/plot 2.png (plot)"
# [1] "x/plot_list/plot 3.png (plot)"
# [1] "x/data_list/1.txt (df)"
# [1] "x/data_list/2.txt (df)"
# [1] "x/data_list/3.txt (df)"
# [1] "x/data_list/4.txt (df)"

Note that this does assume the directory already exists. If you need to check first, see this question for possible solutions.

Thank you MrFlick! – Jan-Benedikt Jagusch Mar 22 '17 at 00:49 — Jan-Benedikt Jagusch, Mar 22 '17 at 00:49

Exporting List Structure to Folder Structure

1 Answers1