lapply and sapply in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the lapply() function do in R?

lapply() applies a function to each element of a list or vector and returns a list of the same length.

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How is sapply() different from lapply()?

sapply() tries to simplify the result of lapply(). It returns a vector or matrix if possible instead of a list.

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What type of output does lapply() always return?

lapply() always returns a list, no matter what the function returns for each element.

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If you want a simplified vector output instead of a list, which function should you use?

Use sapply() because it tries to simplify the output to a vector or matrix when possible.

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Example: What is the output of lapply(1:3, function(x) x^2)?

The output is a list: list(1, 4, 9) because lapply() returns a list of squared numbers.

What does lapply() return when applied to a vector?

A A vector

B A list

C A matrix

D A data frame

lapply() always returns a list, even if the input is a vector.

Which function tries to simplify the output to a vector or matrix?

A sapply()

B tapply()

C apply()

D lapply()

sapply() attempts to simplify the list output from lapply() into a vector or matrix.

What will sapply(1:3, function(x) x^2) return?

A list(1, 4, 9)

B matrix(1,4,9)

C c(1, 4, 9)

D data frame

sapply() returns a vector c(1, 4, 9) by simplifying the list output.

If the function applied returns different types or lengths, what does sapply() return?

A A list

B A simplified vector

C An error

D A matrix

If simplification is not possible, sapply() returns a list just like lapply().

Which function is best when you want to keep the output as a list?

A sapply()

B tapply()

C apply()

D lapply()

lapply() always returns a list, so use it when you want to keep the output as a list.

Explain the difference between lapply() and sapply() in R.

Think about the output type each function returns.

When would you choose lapply() over sapply()?

Consider the structure of the output you need.