Welcome

The Programming with Data course introduces R programming to the Master of Professional Accounting students who have almost zero background in programming. After almost 5 hours of training on R programming, we tried the following Challenging Practice. The good news is that almost all students got it right.

Challenging Practice

I copy the practice question as follows:

Define a function called digits(n) which returns the number of digits of a given integer number. For simplicity, we assume n is zero or positive integer, ie, n >= 0.

• if you call digits(251), it should return 3
• if you call digits(5), it should return 1
• if you call digits(0), it should return 1

For practice, you are required to use if conditions and while loops when necessary. You should use integer division %/% in the while loop to count the number of digits. You are not allowed to use functions such as nchar() and floor().

And here is the suggested solution:

• return 1 if the input number is zero
• else do a while loop to count the number of digits. We will use the integer division for counting.

digits <- function(n) {
  count <- 0
  if (n == 0) {
    return(1)
  } else {
    while (n / 10 >= 0.1) {
      count <- count + 1
      n <- n %/% 10
    }
    return(count)
    }
}

digits(0)

## [1] 1

digits(5)

## [1] 1

digits(251)

## [1] 3

A more general function

If we don’t restrict the input numbers as non-negative integers, we can revise the function as follows. The only change is to make negative numbers as positive and get the integer of a floating number.

digits <- function(n) {
  count <- 0
  n <- abs(as.integer(n))
  if (n == 0) {
    return(1)
  } else {
    while (n / 10 >= 0.1) {
      count <- count + 1
      n <- n %/% 10
    }
    return(count)
    }
}

digits(-15.23)

## [1] 2

digits(-1350.35)

## [1] 4

digits(251.53)

## [1] 3

Of course the nchar() can do it directly.

digits <- function(n) {
  n <- as.character(abs(as.integer(n)))
  return(nchar(n))
}
  
digits(-3800.23)

## [1] 4

digits(-135078.3545)

## [1] 6

digits(259.534)

## [1] 3

Done

To reinforce your understanding of loops in R, you may read and practise this datacamp post.

Happy Coding! And get ready for our next Pop Quiz 😄.