read.csv and write.csv in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the read.csv() function do in R?

read.csv() reads data from a CSV file and loads it into R as a data frame, which is like a table you can work with.

beginner

How do you save a data frame to a CSV file in R?

You use the write.csv() function, which writes the data frame to a CSV file on your computer.

intermediate

What argument do you use in read.csv() to prevent R from converting strings to factors?

Use stringsAsFactors = FALSE to keep text as plain strings instead of factors.

intermediate

What does the row.names = FALSE argument do in write.csv()?

It tells R not to write row numbers as a separate column in the CSV file.

intermediate

If you want to read a CSV file with a different separator, should you use read.csv() or another function?

You should use read.table() with the sep argument, because read.csv() assumes commas as separators.

What is the default separator used by read.csv()?

A Semicolon (;)

B Tab (\t)

C Comma (,)

D Space

read.csv() expects commas as the separator by default.

Which argument in write.csv() prevents writing row names to the file?

A row.names = TRUE

B row.names = FALSE

C header = FALSE

D stringsAsFactors = FALSE

Setting row.names = FALSE stops row numbers from being saved as a column.

How do you read a CSV file without converting text columns to factors?

A Use <code>stringsAsFactors = FALSE</code>

B Use <code>stringsAsFactors = TRUE</code>

C Use <code>header = FALSE</code>

D Use <code>sep = ";"</code>

Use stringsAsFactors = FALSE to keep text as strings.

Which function would you use to read a CSV file with semicolon separators?

A read.table(sep = ";")

B write.csv()

C read.csv()

D readLines()

read.table() lets you specify the separator, so use sep = ";" for semicolons.

What type of object does read.csv() return?

A Matrix

B Vector

C List

D Data frame

read.csv() returns a data frame, which is like a table with rows and columns.

Explain how to read a CSV file into R and save it back after making changes.

Think about loading data, modifying it, then writing it back.

Describe the purpose of the stringsAsFactors argument in read.csv().

Consider how R treats text data by default.