Rolling a Fair 6-Sided Die Until Two Consecutive Rolls Have the Same Value

My task is to simulate rolling a fair 6-sided die until two consecutive rolls have the same value and write a function that approximates the expected value EV. I believe I have most of the program figured out until I reach 'same number' in which I get lost. Please help me find out what to put in place of 'same number' to get my program to work. Here is my block of code:

function EV = hw20(NTrials)
%
%
rng('shuffle)

TotalNRolls = 0;
for Trial = 1:NTrials
    die = randi(6);
    TotalNRolls = TotalNRolls + 1;
     
    while die == 'same number'
            TotalNRolls = TotalNRolls + 1;
    end
end

EV = TotalNRolls/NTrials;

Answer 1

[Ameer Hamza]

Try this code

function EV = hw20(NTrials)
%
%
rng('shuffle')
TotalNRolls = 1;
last_die = inf; % any number other then 1 to 6
while true
    die = randi(6);
    
    if die == last_die || TotalNRolls==NTrials
        break;
    else
        last_die = die;
    end
    TotalNRolls = TotalNRolls + 1;
end
EV = TotalNRolls/NTrials;

end

[Steven Lord]

I'd put the update of TotalNRolls closer to the code that actually rolls the die. That way you could initialize the last_die to the first die roll.

function EV = example603835(NTrials)
rng shuffle
lastRoll = randi(6);
numRolls = 1;

while true
    roll = randi(6);
    numRolls = numRolls + 1;

    if roll == lastRoll
        break   
    end
    lastRoll = roll;    
end
EV = numRolls; % I'm just going to return the number of rolls

The problem summary doesn't mention NTrials at all.

[Ameer Hamza]

Thanks, Steven. Your approach also makes sense for this problem. It is just my guess that NTrials is the maximum number of trials.

[Sophie Culhane]

We have not yet learned 'break' therefore I cannot use that in my program. Thank you for the responses so far.

Answer 2

[Alan Stevens]

I think the above will produce a probability, rather than an expected value. Try

NTrials = 1000;
N = zeros(NTrials,1);
for Trial = 1:NTrials
    
    TotalNRolls = 1;
    die = randi(6);
    keepgoing = true;
    while keepgoing == true
        oldie = die;
        die = randi(6);
        if die == oldie
            keepgoing = false;
        end
        TotalNRolls = TotalNRolls + 1;
    end
    N(Trial) = TotalNRolls;
      
       
end
EV = sum(N)/NTrials;