I want to generate a random number between 1 and 10, but I want the chance of a 10 to be greater

I want to simulate some parts of BlackJack. For wich I need the dealer to draw a random card. Since a jack, a queen and a King are a 10. I have a 4/13 chance of getting a 10. How can I program the 10 to be (4/13) greater and still have it be random ?

Answer 1

[the cyclist]

If you have the Statistics and Machine Learning Toolbox, you can do it like this:

numberSamples = 100;
y = randsample(1:10,numberSamples,true,[1 1 1 1 1 1 1 1 1 4]/13);

Another simple way (that is very intuitive) would be to generate uniform random integers from 1 to 13, and then apply a max of 10.

You can do this as so ...

y = min(10,randi(13,[1 numberSamples]));

Answer 2

[Star Strider]

Another approach:

Deck = repmat([1:10 10 10 10], 130, 1);                         % Create Deck
Deck = Deck(:);                                                 % Create Vector
Tally1 = accumarray(Deck(:), 1);                                % Proof (Delete)
Tens_Pct1 = Tally1(10)/sum(Tally1);                             % Proof (Delete)

idx = randperm(numel(Deck), 4);                                 % Deal Cards Index (4 Cards)
Deal = Deck(idx);                                               % Deal Cards

Tally2 = accumarray(Deal, 1);                                   % Proof (Delete)
Tens_Pct2 = Tally2(10)/sum(Tally2);                             % Proof (Delete)

The ‘Proof’ lines simply demonstrate that the code does what it’s designed to do.

Answer 3

[Roger Stafford]

For n draws, do this:

   r = rand(n,1);
   card = ceil(18*r-10*(r-1/2).*(r>=1/2));

There will be a fifty percent chance of drawing ten (10) through king (13).