read.table and delimiters in R Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of read.table with comma delimiter

What is the output of the following R code when reading a CSV string with read.table using comma as delimiter?

R Programming

text <- "name,age,score\nAlice,30,85\nBob,25,90"
data <- read.table(text = text, sep = ",", header = TRUE)
print(data)

A Error in read.table: no header found

B

  V1  V2  V3
1 name age score
2 Alice 30 85
3 Bob 25 90

C

  name age score
1 Alice  30    85
2   Bob  25    90

D

  name age score
1 Alice 30 85
2 Bob 25 90
3 NA NA NA

💡 Hint

Check the separator and header arguments in read.table.

Using sep="," and header=TRUE correctly reads the CSV data into a data frame with columns name, age, and score.

❓ Predict Output

intermediate

Effect of wrong delimiter in read.table

What will be the output of this R code when reading a tab-separated string but using comma as delimiter?

R Programming

text <- "name\tage\tscore\nAlice\t30\t85\nBob\t25\t90"
data <- read.table(text = text, sep = ",", header = TRUE)
print(data)

A

  V1
1 name\tage\tscore
2 Alice\t30\t85
3 Bob\t25\t90

B

  name age score
1 Alice 30 85
2 Bob 25 90

C Error: sep must be a single character

D

  name\tage\tscore
1 Alice\t30\t85
2 Bob\t25\t90

💡 Hint

What happens if the separator does not match the actual delimiter in the data?

Since sep="," does not match the tab characters, the entire line is read as one column using the first line as the column name "name\tage\tscore".

🧠 Conceptual

advanced

Understanding read.table default delimiter

Which delimiter does read.table use by default if sep is not specified?

A Any whitespace (spaces or tabs)

B Tab ("\t")

C Comma (",")

D Semicolon (";")

💡 Hint

Think about how read.table handles spaces and tabs by default.

By default, read.table treats any whitespace (spaces or tabs) as delimiter if sep is not set.

❓ Predict Output

advanced

Reading data with multiple delimiters

What will be the output of this R code that tries to read data with mixed delimiters using read.table?

R Programming

text <- "name;age,score\nAlice;30,85\nBob;25,90"
data <- read.table(text = text, sep = ";", header = TRUE)
print(data)

A Error in read.table: more columns than header

B

  name age score
1 Alice 30 85
2 Bob 25 90

C

  V1
1 name;age,score
2 Alice;30,85
3 Bob;25,90

D

  name age,score
1 Alice 30,85
2 Bob 25,90

💡 Hint

What happens when sep matches only part of the delimiter pattern?

Using sep=";" splits only on semicolon, so the second column contains the string with comma inside.

❓ Predict Output

expert

Handling missing values with read.table and delimiters

Given this R code reading data with missing values represented by empty fields, what is the output?

R Programming

text <- "name,age,score\nAlice,30,\nBob,,90"
data <- read.table(text = text, sep = ",", header = TRUE, na.strings = "")
print(data)

A

  name age score
1 Alice 30 ""
2 Bob "" 90

B

  name age score
1 Alice 30 NA
2 Bob NA 90

C Error: missing values not allowed

D

  name age score
1 Alice 30 0
2 Bob 0 90

💡 Hint

How does na.strings argument affect empty fields?

Setting na.strings to empty string converts empty fields to NA values in the data frame.