& and | - are element-wise and can be used with vector operations, whereas, || and && always generate single TRUE or FALSE
theck the difference:
> x <- 1:5
> y <- 5:1
> (x > 2) & (y < 3)
[1] FALSE FALSE FALSE TRUE TRUE
> (x > 2) && (y < 3) # here operaand && takes only 1'st elements from logical
# vectors (x>2) and (y<3)
> FALSE
So, && and || are commonly used in if (condition) state_1 else state_2 statements, as
dealing with vectors of length 1