R CSV Files

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.

Syntax

read.csv(file)

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

Example

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

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

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

# Print out information
print(data)

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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

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Writing Files

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

Syntax

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.

Example

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")

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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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