Number of Dice rolling till reaches a Stop Value

Question

I am trying to count the number of dice rolls till it reaches to a definite stop value. For example, I want the stop value as 100. I am writing the following code:

sumofsides <- function(stopvalue) {
  totalsum <- 0
  while (totalsum < stopvalue) {
    face <- sample(6, 1, replace= TRUE)
    totalsum <- totalsum + face
  }
  return(total value)
}

sumofsides(100)
[1] 103

When I am writing the following code to get the number of rolling till it reaches to the stop value. But it's always giving value of 1 which is wrong.

numofrolls <- function(stopvalue) {
  totalsum <- 0
  while (totalsum < stopvalue) {
    face <- sample(6, 1, replace= TRUE)
    totalsum <- totalsum + face
  }
  return(length(face))
}

numofrolls(100)
[1] 1

Any help is appreciated.

Answer 1

In your current loop, you are rewriting totalsum every iteration with a new value, so its length will never go beyond one. One solution would be to use a second variable to count the number of rolls:

rollUntil <- function(n) {
        nRolls   <- 0
        sumRolls <- 0
        while (sumRolls <= n) {
                sumRolls <- sumRolls + sample.int(6, 1)
                nRolls = nRolls + 1
        }
        return(nRolls)
}


# let's look at the distribution of rolls till 100:
hist(replicate(1000,rollUntil(100)))