What is recycling in R
Recycling is when an object is automatically extended in certain operations to match the length of another, longer object.
For example, the vectorised addition results in the following:
c(1,2,3) + c(1,2,3,4,5,6)
[1] 2 4 6 5 7 9
Because of the recycling, the operation that actually happened was:
c(1,2,3,1,2,3) + c(1,2,3,4,5,6)
In cases where the longer object is not a multiple of the shorter one, a warning message is presented:
c(1,2,3) + c(1,2,3,4,5,6,7)
[1] 2 4 6 5 7 9 8
Warning message:
In c(1, 2, 3) + c(1, 2, 3, 4, 5, 6, 7) :
longer object length is not a multiple of shorter object length
Another example of recycling:
matrix(nrow =5, ncol = 2, 1:5 )
[,1] [,2]
[1,] 1 1
[2,] 2 2
[3,] 3 3
[4,] 4 4
[5,] 5 5