Let's take an example of adding a value to a range (as it could be done in a loop for example):
 4 5 6 7 8
This is because the range operator
: has higher precedence than addition operator
What happens during evaluation is as follows:
3+c(1, 2, 3, 4, 5)expansion of the range operator to make a vector of integers.
c(4, 5, 6, 7, 8)Addition of 3 to each member of the vector.
To avoid this behavior you have to tell the R interpreter how you want it to order the operations with
( ) like this:
Now R will compute what is inside the parentheses before expanding the range and gives:
 4 5