CODEWITHSUNDEEP
vbaexcel
alf.cz
alf.cz

Reputation: 59

Round function VBA EXCEL

I need simulate classic play cube (values 1-6) by Rnd function. My solution is Round(5 * Rnd() + 1, 0) , but when I generate 1 milion values, I have not good results (by picture). RESULTS HERE I think, that problem is in bad use of ROUND function, but I do not know where. Thank you for your answers...

Upvotes: 1

Views: 216

Answers (2)

Solar Mike
Solar Mike

Reputation: 8375

Have you tried randbetween() ?? worked fine for me...

Upvotes: 1

bobajob
bobajob

Reputation: 1192

Let's look at this piece-by-piece.

Rnd() gives a number between 0 and 1.

So 5 * Rnd() + 1 gives a number between 1 and 6.

We can think of this number as being equally likely to be in one of 10 half-integer areas: [1,1.5], [1.5,2]...[5.5,6].

One of these will round to 1 - [1,1.5].

Two of these will round to 2 - [1.5,2] and [2,2.5].

3, 4 and 5 similarly have two of these which will round to them.

One of these will round to 6 - [5.5,6]

This explains the distribution you're seeing.

Therefore Round(6 * Rnd() + 0.5, 0) should give you what you're looking for as it extends the area by half in both directions, so gives 1 and 6 the correct weightings.

Upvotes: 5

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