It is common that the logic of a program is not perfectly sequential but contains several branches dependent on certain conditions. Therefore, one of the most basic constructs of a typical programming language is its conditional expressions. In R, if
can be used to branch the logic flow by logical conditions.
Like many other programming languages, the if
expression works with a logical condition. In R, a logical condition is represented by an expression producing a single-element logical vector. For example, we can write a simple function check_positive
that returns 1
if a positive number is provided and nothing otherwise:
check_positive <- function(x) { if (x > 0) { return(1) } }
In the preceding function, x > 0
is the condition to check. If the condition is satisfied, then the function returns 1
. Let's verify the function with various inputs:
check_positive(1) ## [1] 1 check_positive(0...