sapply() function
sapply() function takes list, vector or data frame as input and gives output in vector or matrix. It is useful for operations on list objects and returns a list object of same length of original set. Sapply function in R does the same job as lapply() function but returns a vector.
sapply(X, FUN) Arguments: -X: A vector or an object -FUN: Function applied to each element of x
We can measure the minimum speed and stopping distances of cars from the cars dataset.
dt ← cars lmn_cars ← lapply(dt, min) smn_cars ← sapply(dt, min) lmn_cars
Output:
$speed ## [1] 4 ## $dist ## [1] 2
smn_cars
Output:
speed dist ## 4 2
lmxcars ← lapply(dt, max) smxcars ← sapply(dt, max) lmxcars
Output:
$speed ## [1] 25 ## $dist ## [1] 120
smxcars
Output:
speed dist ## 25 120
We can use a user built-in function into lapply() or sapply(). We create a function named avg to compute the average of the minimum and maximum of the vector.
avg ← function(x) { ( min(x) + max(x) ) / 2} fcars ← sapply(dt, avg) fcars
Output
speed dist ## 14.5 61.0
Sapply in R is more efficient than lapply() in the output returned because sapply() store values direclty into a vector. In the next example, we will see this is not always the case.
