Export a List of Data Frames with Hierarchical Directory Management

Exports every element of a named (or unnamed) list of data.frame / data.table objects to txt or csv files. Element names may contain forward-slashes (/) to encode arbitrary subdirectory depth, e.g. "group_a/subject_01/results" writes <export_path>/group_a/subject_01/results.txt. Unnamed elements are automatically labelled split_<i>.

export_list(split_dt, export_path = tempdir(), file_type = "txt")

Arguments

split_dt

A non-empty list whose elements are data.frame, data.table, or any object coercible via data.table::as.data.table().

export_path

Single character string - the root export directory. Created recursively if absent. Defaults to tempdir().

file_type

"txt" (tab-separated, default) or "csv" (comma-separated). Case-insensitive.

Value

An invisible named character vector of the absolute file paths written, with length equal to the number of successfully exported elements. The total count is accessible via length() on the return value.

Details

Performance design:

• All element names are resolved and path components split in a single vectorised pass before the write loop, so no string work occurs inside the hot path.

• Unique subdirectories are collected and created in one batch (k dir.create() syscalls, where k \(\le\) n).

• The field separator is resolved once at function entry.

• as.data.table() on an existing data.table is a reference-pass (no copy).

Error handling: Individual element failures emit a warning and are skipped; the remaining elements continue to be processed.

Dependencies

Requires the data.table package.

See also

fwrite

Examples

# Example: Export split data to files

# Step 1: Create split data structure
dt_split <- w2l_split(
  data = iris,              # Input iris dataset
  cols2l = 1:2,             # Columns to be split
  by = "Species"            # Grouping variable
)

# Step 2: Export split data to files
export_list(
  split_dt = dt_split       # Input list of data.tables
)
#> [ export_list ] Export complete. 6 / 6 file(s) written to: /tmp/RtmpMDr3j5
# Returns the number of files created
# Files are saved in tempdir() with .txt extension

# Check exported files
list.files(
  path = tempdir(),         # Default export directory
  pattern = "txt",          # File type pattern to search
  recursive = TRUE          # Search in subdirectories
)
#> [1] "Sepal.Length_setosa.txt"     "Sepal.Length_versicolor.txt"
#> [3] "Sepal.Length_virginica.txt"  "Sepal.Width_setosa.txt"     
#> [5] "Sepal.Width_versicolor.txt"  "Sepal.Width_virginica.txt"  

# Clean up exported files
files <- list.files(
  path = tempdir(),         # Default export directory
  pattern = "txt",          # File type pattern to search
  recursive = TRUE,         # Search in subdirectories
  full.names = TRUE         # Return full file paths
)
file.remove(files)          # Remove all exported files
#> [1] TRUE TRUE TRUE TRUE TRUE TRUE