Function dividing a number in n integer with app. same size

问题

I have a number, for instance 10. I want to split this number in 5 integers using something like this:

foo <- function(x, n) rep(x/n, n)
foo(10, 5)
[1] 2 2 2 2 2

This works until x is not a mutliple of n:

foo(10, 3)
[1] 3.333333 3.333333 3.333333

In this case I woud like an output like.

[1] 3 4 3  # the order doesn't matter.

The difference between each integer have to be minimal. So this result is not allowed:

[1] 2 5 3

So far I'm using this function, but not sure whether this is always correct:

foo <- function(x, n){ 
     res <- rep(x/n, n)
     res <- floor(res)  # rounding
     Diff <- x-sum(res)  # Difference of the sum to the input 
     gr <- sample(1:n, Diff) # select by chance as many values as `Diff` is
     res[gr] <- res[gr]+1 # plus one
     res   
  }

回答1:

Your function should work but will give a different answer every time. Also you probably want to use the Euclidian division for that, which is what you a trying to mimcik with floor and Diff. In R you get the quotient with %/% and the remainder with %% So a simple solution could be

foo <- function(x,n)
{
    res=numeric(n)
    a=x%/%n # the quotient
    b=x%%n # the remainder
    res[1:n]=a # fill with the quotient
    if(b>0){
     for(i in 1:b)
        res[n-i+1]=res[n-i+1]+1 # add as many time a one in a cell as needed by the remainder
     }
    return(res)
}

回答2:

This I thought was an intriguing question. I figured out that the remainder indicates the number of (quotient+1) numbers you have. For example:

17/7 = 2 + 3/7 --> So you need (7-3) x 2 and 3 x (2+1)

19/7 = 2 + 5/7 --> So you need (7-5) x 2 and 5 x (2+1)

Leading to a more elegant solution:

  foo <- function(x,n){
     a = x%/%n # the quotient
     b = x%%n  # the remainder
     return(c(rep(a,n-b),rep(a+1,b)))
}

回答3:

This should work:

foo <- function(x, n) rep(x%/%n, n) + sample(c(rep(1, x %% n), rep(0, n - x %% n)), n)

foo(10, 5)
[#1] 2 2 2 2 2
foo(10, 3)
#[1] 3 3 4

来源：https://stackoverflow.com/questions/41997162/function-dividing-a-number-in-n-integer-with-app-same-size

标签

integer

division