<- lapply(i, FUN)
result
# compared to:
<- c()
result for(i in x){
<- FUN
result[i] }
lapply-loops
R has some more specific loop types that work very well with vectors
and lists
. They are called lapply
loops in R and make use of functions
that are applied over the element of a vector
or list
.
The syntax of the lapply
loop can be a bit confusing at first as it is the other way around as the for
loop. The biggest difference is, that lapply
returns a list of values for every iteration step. So the output of the loop can be assigned directly to a variable.
lapply() # list apply
sapply() # apply with vector output
apply() # loop over rows or columns of a data.frame
sapply(seq(10), function(x){
^2
x })
[1] 1 4 9 16 25 36 49 64 81 100