I need my code to work/dont know what is going wrong.

I am working on a MATLAB assignment where I need to create a custom function called r_wheel.

The function should:

• Take two inputs: bet_color and bet_amount
• Return three outputs:
• result_message (string saying if the bettor won or lost)
• winner (0 if lost, 1 if won)
• wager_message (string saying how much money was won or lost)

The payout rules are:

• Red/Black → 1:1 payout
• Green → 17:1 payout
• If the bettor loses, they lose the amount wagered.

After that, I need to write a script that runs the function 100 times betting on "red" and calculates the odds of winning.

My issue is that I am not understanding how to get the function to be repeated multiple times and also add to a separate counter.

The error message I get is (Index exceeds the number of array elements. Index must not exceed 1.) Also, the code does not add to a counter, it instead only displays the answer one time.

This is the code for the function I made

function [result_msg,winner,wager_message] = r_wheel(bet_color, bet_amount)
disp('Spinning...')
pause(2) %delay for suspense
random_int=randi([1 38]); %random # between 1 and 38
if random_int < 3 % if the # is less 1 or 2 then result is green
    result_color = 'Green'
    wager_message = bet_amount*17 + bet_amount;
elseif (random_int <21) && (random_int>2) 
    result_color = 'Red' % if # is between 3 and 20 result is red
    wager_message = bet_amount*2;
else 
    result_color = 'Black' %if # is between 21 and 38 the result is black
    wager_message = bet_amount*2;
end

disp(result_color)

if strcmp(result_color, bet_color) % using string compare function to chekc if strings are the same
    result_msg = 'Congratulations! You win!'; % if bet color is correct set result to win
    winner = 1; %set winner variable to 1
    wager_message = wager_message
else
    result_msg = 'Sorry, you lose. Better luck next time!'; %if the bet color is not the same as result color set message
    winner = 0; %set winner variable to 0
    wager_message = -bet_amount
end
end 

And here is the code for the loop.

clc, clear
x='Red'
y= 15
win_count = 0
for i = 1:100
    [result,winner]=r_wheel(x, y) % runs the function
    win_count = 0
    [result,winner]=r_wheel(x, y)
    if winner(i)==1
        win_count(i) = win_count(i)+1
    else 
        win_count(i)= win_count(i)
    end
end
disp(win_count)
disp(result)

Answer 1

[Stephen23]

Explanation

There are a few clear bugs causing your problems. Let me walk through each one.

Bug 1: The function is called twice per iteration

You call r_wheel twice inside the loop, which means it spins the wheel twice but only keeps the second result.

Bug 2: win_count is reset to 0 inside the loop

By writing win_count = 0 inside the for loop, you wipe out the count every single iteration, so it never accumulates.

Bug 3: winner(i) causes the index error

winner is returned from your function as a single scalar value (0 or 1), not an array. When i reaches 2, MATLAB tries to access winner(2), which doesn't exist, causing the "Index exceeds the number of array elements" error. Same problem applies to win_count(i).

Solution

x = 'Red';
y = 15;
win_count = 0; % Initialize OUTSIDE the loop
N = 4; % 100

for k = 1:N
    [result, winner, wager] = r_wheel(x, y); % Call the function ONCE per iteration
    win_count = win_count + (winner == 1);
end

Spinning...
Red
Spinning...
Black
Spinning...
Black
Spinning...
Red

fprintf('Out of %d spins, you won %d times.\n', k, win_count);

Out of 4 spins, you won 2 times.

fprintf('Estimated probability of winning: %.2f%%\n', (win_count / k) * 100);

Estimated probability of winning: 50.00%

Function Too

The function has a few small issues worth cleaning up as well:

function [result_msg, winner, wager_message] = r_wheel(bet_color, bet_amount)
    disp('Spinning...')
    pause(2)

    random_int = randi([1 38]);

    if random_int <= 2
        result_color = 'Green';
        wager_message = bet_amount * 17 + bet_amount; % win = 17:1 payout + original bet back
    elseif random_int <= 20
        result_color = 'Red';
        wager_message = bet_amount * 2; % win = 1:1 payout + original bet back
    else
        result_color = 'Black';
        wager_message = bet_amount * 2;
    end

    disp(result_color)

    if strcmp(result_color, bet_color)
        result_msg = 'Congratulations! You win!';
        winner = 1;
        % wager_message already set above
    else
        result_msg = 'Sorry, you lose. Better luck next time!';
        winner = 0;
        wager_message = -bet_amount; % Lose the wagered amount
    end
end

[Joshua]

Thank you very much, I am not sure how I didnt even think of trying that, much appreciated!