Type checking and conversion in R Programming - Mini Project: Build & Apply

Type Checking and Conversion in R

📖 Scenario: You are working with a small dataset that contains different types of information. You need to check the types of these data and convert them to the correct types for further analysis.

🎯 Goal: Learn how to check the type of variables and convert them to other types in R.

📋 What You'll Learn

Create variables with specific values and types

Check the type of each variable using class()

Convert variables to different types using as.character(), as.numeric(), and as.logical()

Print the results to see the changes

💡 Why This Matters

🌍 Real World

Data scientists and analysts often receive data in mixed types and need to check and convert types before analysis.

💼 Career

Understanding type checking and conversion is essential for data cleaning, preprocessing, and ensuring correct data manipulation in R programming jobs.

1

Create variables with different types

Create three variables in R: num_var with the numeric value 42, char_var with the character string "100", and log_var with the logical value TRUE.

R Programming

# Create variables num_var, char_var, and log_var with the specified values
# Your code here

Hint

Use the assignment operator <- to create variables.

2

Check the types of the variables

Use the class() function to check the type of each variable: num_var, char_var, and log_var. Assign the results to variables type_num, type_char, and type_log respectively.

R Programming

num_var <- 42
char_var <- "100"
log_var <- TRUE
# Use class() to check types and assign to type_num, type_char, and type_log
# Your code here

Hint

Use class(variable) to get the type of a variable.

3

Convert variables to different types

Convert num_var to a character and assign it to num_to_char. Convert char_var to numeric and assign it to char_to_num. Convert log_var to numeric and assign it to log_to_num.

R Programming

num_var <- 42
char_var <- "100"
log_var <- TRUE
type_num <- class(num_var)
type_char <- class(char_var)
type_log <- class(log_var)
# Convert types as instructed and assign to new variables
# Your code here

Hint

Use as.character(), as.numeric() to convert types.

4

Print the types and converted values

Print the variables type_num, type_char, type_log, and the converted variables num_to_char, char_to_num, log_to_num using print().

R Programming

num_var <- 42
char_var <- "100"
log_var <- TRUE
type_num <- class(num_var)
type_char <- class(char_var)
type_log <- class(log_var)
num_to_char <- as.character(num_var)
char_to_num <- as.numeric(char_var)
log_to_num <- as.numeric(log_var)
# Print all type and converted value variables
# Your code here

Hint

Use print(variable) to show the values.

Practice

1. Which function in R checks if a variable is of numeric type?

easy

A. as.character()

B. as.numeric()

C. is.character()

D. is.numeric()

Solution

1. Step 1: Understand type checking functions

   Functions starting with is. check the type of a variable.

2. Step 2: Identify the correct function for numeric check

   is.numeric() returns TRUE if the variable is numeric.

3. Final Answer:

   is.numeric() -> Option D

4. Quick Check:

   Type check numeric = is.numeric() [OK]

Hint: Use is.type() to check type, as.type() to convert [OK]

Common Mistakes:

• Confusing is.numeric() with as.numeric()
• Using as.character() to check type
• Using is.character() for numeric check

2. Which of the following is the correct way to convert a character vector c("1", "2", "3") to numeric in R?

easy

A. is.numeric(c("1", "2", "3"))

B. as.numeric(c("1", "2", "3"))

C. as.character(c(1, 2, 3))

D. is.character(c(1, 2, 3))

Solution

1. Step 1: Identify conversion functions

   as.numeric() converts data to numeric type.

2. Step 2: Apply conversion to character vector

   Using as.numeric(c("1", "2", "3")) converts strings to numbers 1, 2, 3.

3. Final Answer:

   as.numeric(c("1", "2", "3")) -> Option B

4. Quick Check:

   Convert char to numeric = as.numeric() [OK]

Hint: Use as.numeric() to convert strings to numbers [OK]

Common Mistakes:

• Using is.numeric() instead of as.numeric()
• Trying to convert numeric to character for numeric conversion
• Confusing is.character() with conversion functions

3. What will be the output of the following R code?

vec <- c("10", "20", "30")
num_vec <- as.numeric(vec)
is.numeric(num_vec)

medium

A. TRUE

B. FALSE

C. Error

D. NA

Solution

1. Step 1: Convert character vector to numeric

   as.numeric(vec) changes strings "10", "20", "30" to numbers 10, 20, 30.

2. Step 2: Check if converted vector is numeric

   is.numeric(num_vec) returns TRUE because num_vec is numeric.

3. Final Answer:

   TRUE -> Option A

4. Quick Check:

   as.numeric() converts, is.numeric() confirms [OK]

Hint: as.numeric() converts, is.numeric() checks type [OK]

Common Mistakes:

• Expecting FALSE because original was character
• Thinking as.numeric() returns character
• Confusing is.numeric() with as.numeric()

4. Identify the error in the following R code snippet:

val <- "123abc"
num_val <- as.numeric(val)
print(num_val)

medium

A. No error, prints 123

B. Syntax error due to quotes

C. Prints NA with a warning

D. Prints 0 without warning

Solution

1. Step 1: Attempt to convert mixed string to numeric

   as.numeric("123abc") cannot convert because of non-numeric characters.

2. Step 2: Result of conversion

   It returns NA and shows a warning about NAs introduced by coercion.

3. Final Answer:

   Prints NA with a warning -> Option C

4. Quick Check:

   Invalid numeric conversion = NA + warning [OK]

Hint: Invalid numeric strings convert to NA with warning [OK]

Common Mistakes:

• Expecting partial numeric conversion
• Ignoring warning messages
• Assuming syntax error due to quotes

5. You have a list lst <- list("5", 10, "abc", "15.5"). Which R code correctly converts all elements to numeric, replacing non-convertible values with 0?

hard

A. sapply(lst, function(x) if(is.na(as.numeric(x))) 0 else as.numeric(x))

B. sapply(lst, function(x) as.numeric(x))

C. sapply(lst, function(x) if(is.na(as.numeric(x))) as.numeric(x) else 0)

D. sapply(lst, function(x) if(is.numeric(x)) x else 0)

Solution

1. Step 1: Convert each element to numeric and check for NA

   Use as.numeric(x) inside a function and check if result is NA.

2. Step 2: Replace NA with 0, else keep numeric value

   If as.numeric(x) is NA, return 0; otherwise return the numeric value.

3. Final Answer:

   sapply(lst, function(x) if(is.na(as.numeric(x))) 0 else as.numeric(x)) -> Option A

4. Quick Check:

   Replace NA with 0 using conditional inside sapply [OK]

Hint: Use is.na(as.numeric(x)) to detect and replace [OK]

Common Mistakes:

• Not checking for NA after conversion
• Replacing numeric values incorrectly
• Confusing condition logic in if-else