CSV Files

Published Oct 7, 2022Updated Mar 8, 2023
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Data within CSV files can be read and written to using the read.csv() and write.csv() functions.

Reading Data

The read.csv() function reads data from a CSV file.



A file with a .csv extension is read from the read.csv() function.


Suppose there is a students.csv file with the following data in it:

First Name Last Name Grade ID
Rita Aros 3 N76654
Noah Chen 1 N75435
Averill Freeman 9 N43542
Stephen Holmes 11 N97543
Blake Jones 12 N85342
Francesca Mahone 8 N49854
Katelyn Miller 2 N58632
Martin Phillman 5 N86873
Carl Sanchez 4 N43263
April Tillman 7 N63430
Tori Vega 10 N76543
Frank Williams 3 N86532
Robert Ye 10 N67541

The data can be retrieved using the read.csv() function and then printed:

# Reading csv files
data <- read.csv("students.csv")
# Print out information

This reads the data in as a data frame. The output would be the following:

First.Name Last.Name Grade ID
1 Rita Aros 3 N76654
2 Noah Chen 1 N75435
3 Averill Freeman 9 N43542
4 Stephen Holmes 11 N97543
5 Blake Jones 12 N85342
6 Francesca Mahone 8 N49854
7 Katelyn Miller 2 N58632
8 Martin Phillman 5 N86873
9 Carl Sanchez 4 N43263
10 April Tillman 7 N63430
11 Tori Vega 10 N76543
12 Frank Williams 3 N86532
13 Robert Ye 10 N67541

Writing Files

The write.csv() function can be used to write data into CSV files.


write.csv(data, file)
  • data: The information to write into the .csv file.
  • file: Name of the file with a .csv extension to write the data into.


The following example uses the subset() function to retrieve students that are above grade 8 from the students.csv file. Then it writes the subset into the highSchoolers.csv file using the write.csv() function:

# Retrieve data from CSV file
data <- read.csv("students.csv")
# Get subset of students in grades higher than 8
higherGrades <- subset(data, Grade > 8)
# Write the subset into a new CSV file
write.csv(higherGrades, "highSchoolers.csv")

The example above will return the highSchoolers.csv file with the following data in it:

First.Name Last.Name Grade ID
3 Averill Freeman 9 N43542
4 Stephen Holmes 11 N97543
5 Blake Jones 12 N85342
11 Tori Vega 10 N76543
13 Robert Ye 10 N67541

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