The lapply() function in R can be used to apply a function to each element of a list, vector, or data frame and obtain a list as a result.

The sapply() function can also be used to apply a function to each element of a list, vector, or data frame but it returns a vector as a result.

The following examples show how to use each of these functions in R.

Example: How to Use lapply() in R

The following code shows how to use the lapply() function to multiply each value in each column of a data frame by 2:

#create data frame
df <- data.frame(x=c(1, 2, 2, 3, 5),
                 y=c(4, 4, 6, 7, 8),
                 z=c(7, 7, 9, 9, 9))

#view data frame
df

  x y z
1 1 4 7
2 2 4 7
3 2 6 9
4 3 7 9
5 5 8 9

#multiply each value in each column by 2
lapply(df, function(df) df*2)

$x
[1]  2  4  4  6 10

$y
[1]  8  8 12 14 16

$z
[1] 14 14 18 18 18

Notice that the result is a list.

Example: How to Use sapply() in R

The following code shows how to use the sapply() function to multiply each value in each column of a data frame by 2:

#create data frame
df <- data.frame(x=c(1, 2, 2, 3, 5),
                 y=c(4, 4, 6, 7, 8),
                 z=c(7, 7, 9, 9, 9))

#view data frame
df

  x y z
1 1 4 7
2 2 4 7
3 2 6 9
4 3 7 9
5 5 8 9

#multiply each value in each column by 2
sapply(df, function(df) df*2)

      x  y  z
[1,]  2  8 14
[2,]  4  8 14
[3,]  4 12 18
[4,]  6 14 18
[5,] 10 16 18

Notice that the result is a matrix of vectors.

Note that you can use as.data.frame() to return a data frame as a result instead of a matrix:

#multiply each value in each column by 2 and return a data frame
as.data.frame(sapply(df, function(df) df*2))

   x  y  z
1  2  8 14
2  4  8 14
3  4 12 18
4  6 14 18
5 10 16 18

When to Use lapply() vs. sapply()

In 99% of cases, you’ll use sapply() because it makes the most sense to return a vector or matrix as a result.

However, in some rare circumstances you may need to use lapply() instead if you need the result to be a list.

Note that sapply() and lappy() perform the same operations on a vector, matrix, or data frame. The only difference is the class of the object that is returned.