27.12 Function Guidelines

20200105

Functions should be no longer than a screen or a page. Long functions generally suggest the opportunity to consider more modular design. Take the opportunity to split the larger function into smaller functions.

When referring to a function in text include the empty round brackets to make it clear it is a function reference as in rpart().

Generally prefer a single base::return() from a function. Understanding a function with multiple and nested returns can be difficult. Sometimes though, particularly for simple functions as in the alternative below, multiple returns work just fine.

**Preferred**

factorial <- function(x)
{
  if (x==1)
  {
    result <- 1
  }
  else
  { 
    result <- x * factorial(x-1)
  }

  return(result)
}

**Alternative**

factorial <- function(x)
{
  if (x==1)
  {
    return(1)
  }
  else
  {
    return(x * factorial(x-1))
  }
}

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