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DoSS Toolkit

51 File creation and manipulation

http://theautomatic.net/2018/07/11/manipulate-files-r/

Written by Haoluan Chen and last updated on 7 October 2021.

51.1 Introduction

In this lesson, you will learn how to:

Prerequisite skills include:

  • Setup RStudio.
  • Folder set up.

Highlights:

Manipulation folders and files on your computer using R

51.2 dir.create()

dir.create() function allows you to create new folders in your current directory or desired file path. It takes in a string parameter that is either the name of the new folder or the file path that including the name of the new folder.

You can run the following code to create a new folder in your current directory called “New folder.”

dir.create("New folder")
#> Warning in dir.create("New folder"): 'New folder' already
#> exists

Alternatively, you can specify the path of the new folder. It can be anywhere on your computer! Using the following code, I created a folder called “New” on my desktop. Paths can be different for different computer systems.

dir.create("/Users/chl19/Desktop/New")
#> Warning in dir.create("/Users/chl19/Desktop/New"): cannot
#> create dir '/Users/chl19/Desktop/New', reason 'No such file
#> or directory'

51.3 file.create()

file.create() function allows you to create a new file in your current directory or desired file path. It takes in a string parameter that is either the new file’s name or the file path.

The following code creates a new text file in your current directory.

file.create("new_textfile.txt")
#> [1] TRUE

The output TRUE means the file is created.

Like dir.create, you can create a file anywhere on your computer by inputting the file path!

file.create("/Users/chl19/Desktop/another_new_textfile.txt")
#> Warning in file.create("/Users/chl19/Desktop/
#> another_new_textfile.txt"): cannot create file '/Users/
#> chl19/Desktop/another_new_textfile.txt', reason 'No such
#> file or directory'
#> [1] FALSE

51.4 file.exists()

file.exists() function allow you to check if a file exists in your current directory or the specified path. It takes in a string parameter that is same as dir.create() and file.create(). It will output a boolean indicating if the file there exists file in the directory.

For example, I can check if I have successfully created the “new_textfile.txt.”

file.exists("new_textfile.txt")
#> [1] TRUE

Let’s try checking a file that does not exist in the current directory!

file.exists("a_file.txt")
#> [1] FALSE

Checking file that is outside of our working directory (This is the file we created above!).

file.exists("/Users/chl19/Desktop/another_new_textfile.txt")
#> [1] FALSE

51.5 file.remove()

file.remove() can be used to remove(delete) files in your directory or specified file path. It takes in a string parameter that is either the new file’s name or the file path. It will return a boolean indicating if you have successfully removed the file.

Let’s try to remove the new_textfile we just created in our directory.

file.remove("new_textfile.txt") 
#> [1] TRUE

Let’s check if the function works properly!

file.exists("new_textfile.txt")
#> [1] FALSE

The “new_textfile.txt” does not exist anymore! We have removed(deleted) the file!

51.6 dirname()

dirname() function can extract your directory path from a file path. It takes a string that is your file path.

For example, let’s first create a new file

file.create("newfile.txt")
#> [1] TRUE

This new file has following file path: “C:/Users/a/chl19/Desktop/doss_toolkit_book/newfile.txt”

dirname("C:/Users/a/chl19/Desktop/doss_toolkit_book/newfile.txt")
#> [1] "C:/Users/a/chl19/Desktop/doss_toolkit_book"

When we input this file path in dirname(), it will return the path of our current directory!

51.7 basename()

As we see that dirname() extracts the directory path from the full file path, the function basename extracts the file name from the full file path.

basename("C:/Users/a/chl19/Desktop/doss_toolkit_book/newfile.txt")
#> [1] "newfile.txt"

Here, we get the file name using basename().

51.8 file.path()

The file.path() function allows you to create reproducible code that can be run in different operating systems such as macOS or windows since different operating systems have different directory separators.

The file.path() function takes in a set of strings that you want to paste together to a file path. And another parameter is called fsep, which is the path separator in string format.

For example, in windows, our path is separated by /.

“C:/Users/a/chl19/Desktop/doss_toolkit_book/newfile.txt”

We can generate the file path above using file.path function:

file.path("c:", "Users", "a", "chl19", "Desktop", "doss_toolkit_book", "newfile.txt", fsep="/")
#> [1] "c:/Users/a/chl19/Desktop/doss_toolkit_book/newfile.txt"

If the operating system uses \\ as the path separator, we can generate the file path using the following code.

file.path("c:", "Users", "a", "chl19", "Desktop", "doss_toolkit_book", "newfile.txt", fsep="\\")
#> [1] "c:\\Users\\a\\chl19\\Desktop\\doss_toolkit_book\\newfile.txt"

51.9 Exercises

51.9.1 Exercises 1

Write a function that takes in a file name and checks if this file exists in your current directory. If this file exists in your current directory, print “The file already exists.” If this file is not in your current directory, create the file and print “File created.” (There are multiple answers!)

51.9.2 Exercises 2

Please create a new folder called “my_data” in your current directory, then create a new CSV file called data in this “data” folder.

51.9.3 Exercises 3

Check if you successfully created the data.csv file in my_data folder from exercise 2

51.9.4 Exercises 4

Please remove the data.csv file you created in exercies 2

51.9.5 Exercises 5 

file.path("c:", "Users", "doss_toolkit_book", "totally_addicted_to_base", fsep="/")
#> [1] "c:/Users/doss_toolkit_book/totally_addicted_to_base"

51.10 Common mistakes & errors

  • Make sure the path is correct.

  • filename is not case sensitive. (i.e “newfile.txt” is same as "Newfile.txt) For example:

file.create("Hi.txt")
#> [1] TRUE
file.exists("hi.txt")
#> [1] TRUE
file.remove("hi.txt")
#> [1] TRUE

We see that after we created “Hi.txt,” the file.exists("hi.txt") returned TRUE, which means the file name is not case-sensitive. This also reflects when we run file.remove("hi.txt") that we successfully remove the file “Hi.txt” that we just created.

51.11 Next steps

This website contains more function for file manipulation http://theautomatic.net/2018/07/11/manipulate-files-r/

RDocumentation for file manipulation https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/files

RDocumentation for Manipulation of Directories https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/files2

51.12 Exercises

51.12.1 Question 1

dir.create creates files in your current directory. a. True b. False

51.12.2 Question 2

What does it mean when file.create() returns True? a. File is created b. Folder is created c. File is already in your directory d. Fail to create the file

51.12.3 Question 3

file.exists() function allow you to check if a file exists in your current directory or the specified path. a. True b. False

51.12.4 Question 4

What is the output of file.exists()? a. A boolean b. String “Yes” and “No” c. String “True” and "False d. number 1 and 0

51.12.5 Question 5

file.remove() can be used to remove(delete) files in your directory or specified file path. a. True b. False

51.12.6 Question 6

What is the output for following code? dirname("C:/Users/Desktop/newfile.txt") a. “C:” b. “C:/Users” c. “C:/Users/Desktop” d. “C:/Users/Desktop/newfile.txt”

51.12.7 Question 7

What is the output for following code? basename("C:/Users/Desktop/newfile.txt") a. “C:” b. “C:/Users” c. “C:/Users/Desktop/newfile.txt” d. “newfile.txt”

51.12.8 Question 8

dirname() return the path of our current directory! a. True b. False

51.12.9 Question 9

basename() extracts the directory name from the full file path. a. True b. False

51.12.10 Question 10

file.path("c:", "Users", "doss_toolkit_book", "totally_addicted_to_base", fsep="/")

“What is the output of above code?” a. “c:/Users/doss_toolkit_book/totally_addicted_to_base” b. “totally_addicted_to_base” c. TRUE d. “c:/Users/doss_toolkit_book”