Extracting File Names in R

How to extract file names in R with basename() and file.path_sans_ext().

Note

Original Japanese version: Rでファイル名を抽出する方法

When handling file paths in R, you may want to extract only the file name or obtain the file name without its extension. This article summarizes how to extract file names in R using basename() and tools::file_path_sans_ext().

Extracting the File Name

Use the basename() function to extract a file name from a file path.

file_path <- "/path/to/your/file/data.csv"
file_name <- basename(file_path)
print(file_name)

[1] "data.csv"

The file name alone is extracted from the file path that includes the directory path.

Extracting the File Name Without the Extension

Use the file_path_sans_ext() function from the tools package to obtain a file name without its extension.

library(tools)
file_path <- "/path/to/your/file/data.csv"
file_name_no_ext <- file_path_sans_ext(basename(file_path))
print(file_name_no_ext)

[1] "data"

This obtains the file name without the extension.

NoteAbout the Name file_path_sans_ext()

The function name is a little long and hard to remember, but it becomes easier if you remember its meaning. sans is French for “without.” It corresponds to the English word without. Also, ext is short for “extension.” Therefore, file_path_sans_ext() means “file path without extension.”

Example

This is useful when combining data with corresponding image file names and storing them in a data frame.

file_paths <- c(
  "/path/to/your/file/data1.csv",
  "/path/to/your/file/data2.csv",
  "/path/to/your/file/data3.csv"
)
file_names <- basename(file_paths)
file_names_no_ext <- file_path_sans_ext(file_names)
df <- data.frame(value = c(10, 20, 30), file_name = file_names_no_ext)
print(df)

  value file_name
1    10     data1
2    20     data2
3    30     data3

In this way, file names can be included in a data frame.