Conditional expressions

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.

Using if as a statement

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) { 

In the preceding function, ...

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