I am confused about the output from the replicate function in R, I am trying to use it in two different ways, that (in my mind) should give a matrix as output!
so, if I use
replicate(5, seq(1,5,1))
I get a matrix 5x5
[,1] [,2] [,3] [,4] [,5]
[1,] 1 1 1 1 1
[2,] 2 2 2 2 2
[3,] 3 3 3 3 3
[4,] 4 4 4 4 4
[5,] 5 5 5 5 5
..and that's ok, I get that...
but, if I instead use:
replicate(5, for(i in 1:5){print(i)})
I get the following:
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[[1]]
NULL
[[2]]
NULL
[[3]]
NULL
[[4]]
NULL
[[5]]
NULL
can anyone explain me why does this happen? thanks :)
Answer
A for loop returns NULL. So in the second case, the replicate function is executing for(i in 1:5){print(i)} five times, which is why you see all those numbers printed out.
Then it is putting the return values in a list, so the return value of the replicate call is a list of five NULLs, which gets printed out. Executing
x<-replicate(5, for(i in 1:5){print(i)})
x
should clarify.