Ifelse vectorized function in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the ifelse() function do in R?

It checks a condition for each element of a vector and returns a value if TRUE and another if FALSE, all in a vectorized way.

beginner

How does ifelse() handle vectors?

It tests each element of the condition vector separately and returns a vector of the same length with values chosen from the 'yes' or 'no' arguments.

beginner

What is the syntax of ifelse()?

ifelse(test, yes, no)

where test is a logical vector, yes is returned if TRUE, and no if FALSE.

intermediate

Why is ifelse() preferred over a loop for element-wise conditions?

Because it is vectorized, making it faster and simpler to write than looping through each element manually.

intermediate

What happens if the lengths of yes or no arguments differ from the condition vector in ifelse()?

R recycles the shorter vector to match the length of the condition vector, which can lead to unexpected results if not careful.

What does ifelse(c(TRUE, FALSE), 1, 0) return?

A [0, 1]

B [TRUE, FALSE]

C [1, 0]

D [1]

The function returns 1 where condition is TRUE and 0 where FALSE, so the result is [1, 0].

Which of these is TRUE about ifelse() in R?

A It works element-wise on vectors.

B It only works on single TRUE or FALSE values.

C It cannot return vectors.

D It is slower than loops.

ifelse() is vectorized and works element-wise on vectors.

What will ifelse(c(TRUE, FALSE, TRUE), 'yes', 'no') output?

A c('yes', 'no', 'yes')

B c('no', 'yes', 'no')

C c(TRUE, FALSE, TRUE)

D c('yes')

It returns 'yes' for TRUE elements and 'no' for FALSE elements.

If the 'yes' argument is shorter than the condition vector, what does ifelse() do?

A Returns only the first element.

B Recycles the 'yes' vector to match the length.

C Ignores extra elements in the condition.

D Throws an error.

R recycles shorter vectors to match the length of the condition vector.

Which is a good use case for ifelse()?

A Sorting a vector.

B Reading files from disk.

C Creating plots.

D Assigning values based on a condition to each element of a vector.

ifelse() is designed for element-wise conditional assignment.

Explain how the ifelse() function works in R and why it is useful.

Think about how it handles each element of a vector and why that helps.

Describe what happens when the lengths of the 'yes' or 'no' arguments differ from the condition vector in ifelse().

Consider how R handles vectors of different lengths in operations.