Why do sapply() and lapply() have same result?

Question

I am new to R. I was practicing lapply() and sapply() function: lapply() returns list, and sapply() returns as vector/matrix. Now there I don't understand why do lapply() and sapply() have same result as a list?

> x1 <- lapply(list(1:3, 25:29), function(x) {2*x})
> x2 <- sapply(list(1:3, 25:29), function(x) {2*x})
> x1
[[1]]
[1] 2 4 6

[[2]]
[1] 50 52 54 56 58

> x2
[[1]]
[1] 2 4 6

[[2]]
[1] 50 52 54 56 58

> str(x2)
List of 2
 $ : num [1:3] 2 4 6
 $ : num [1:5] 50 52 54 56 58
> mode(x2)
[1] "list"

After, I checked unlist() and it return same input as a vector. It's hard to understand why do sapply() return list type as a result.

Thank you.

[this answer](http://stackoverflow.com/a/7141669/4002530) is worth a read. — tospig, Apr 08 '16 at 08:54

score 5 · Accepted Answer · answered Apr 08 '16 at 08:54

5

If the length of the list elements are not the same, sapply will not coerce it to matrix and will have the same result as lapply

We can check the Usage of ?sapply and ?lapply

lapply(X, FUN, ...)

sapply(X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)

The simplify=TRUE is the one that converts a list of equal length output to a matrix

answered Apr 08 '16 at 08:54

akrun

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Thanks a lot! Now I understand! :D – Jaehee Hur Apr 09 '16 at 07:36

Why do sapply() and lapply() have same result?

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