read.table and delimiters in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the read.table() function in R?

read.table() is used to read data from a file into R as a data frame. It reads tabular data where columns are separated by delimiters.

beginner

Which argument in read.table() specifies the character used to separate columns?

The sep argument defines the delimiter character that separates columns in the input file.

beginner

What is the default delimiter used by read.table() if sep is not specified?

The default delimiter is any whitespace (spaces, tabs). So read.table() treats one or more spaces or tabs as column separators.

intermediate

How do you read a CSV file using read.table()?

Use read.table(file, sep=",", header=TRUE) to read a CSV file where columns are separated by commas and the first row contains column names.

beginner

What does the header argument do in read.table()?

The header argument tells R whether the first line of the file contains column names (header=TRUE) or not (header=FALSE).

What is the default delimiter used by read.table() in R?

A Whitespace (spaces or tabs)

B Comma

C Semicolon

D Colon

The default delimiter for read.table() is whitespace, meaning spaces or tabs separate columns unless you specify otherwise.

Which argument do you use to specify the delimiter in read.table()?

A delimiter

B sep

C delim

D split

The sep argument sets the character that separates columns in the input file.

How do you tell read.table() that the first row contains column names?

A firstrow=TRUE

B names=TRUE

C header=TRUE

D colnames=TRUE

Use header=TRUE to indicate the first row has column names.

Which of these is the correct way to read a comma-separated file with headers using read.table()?

A read.table(file, sep=" ", header=TRUE)

B read.table(file, sep=";", header=FALSE)

C read.table(file, sep="\t", header=FALSE)

D read.table(file, sep=",", header=TRUE)

Comma-separated files require sep="," and if the first row has headers, header=TRUE.

If your data columns are separated by tabs, what should you set sep to in read.table()?

A "\t"

B ","

C ";"

D " "

Tabs are represented by "\t" in R strings, so use sep="\t" for tab-delimited files.

Explain how to use read.table() to read a file where columns are separated by semicolons and the first row contains headers.

Think about how to tell R about the delimiter and headers.

Describe what happens if you use read.table() without specifying the sep argument on a file where columns are separated by commas.

Consider what the default separator is and how it affects reading comma-separated data.