I need to make a long code that already has loops loop.

%I need everything inside the loop (for=k1:L ) to loop L amount of times.
%Each loop should create a new startingpos and do new calculations but it
%does not. The answer (Finalprob) should be an average of all of the loops
%that find probability. It should be average probability, however right now
%it just reprints one value of (probu).
L=10000
for k=1:L
prime=primes(250); %prime numbers less than 250
 Prob_prime=0.85; %setup for prime probability
 Prob_other=0.3;
startingpos=randi(250,1,1) %makes a random number for position between 0-250. START
position=startingpos;
for f=2:15 %for loop for all moves after the first position.
    r=randi(2,1,1);
if (position(f-1)==1) %makes sure that it cannot go to 0
    position(f)=2;
elseif (position(f-1)==250) %makes sure it cant go over 250
    position(f)=249;
elseif (r==1) %makes a 50% chance that it counts up or down.
    position(f)=position(f-1)+1; 
else
    position(f)=position(f-1)-1;
    
    x1=Prob_prime*position(f-1);
 x2=Prob_other*position(f-1);
d1=position(f-1)-x1;
d2=position(f-1)-x2;

end
end
disp('Position = ');
disp(position);
%plot(1:length(position),position)
%xlabel('time')
%ylabel('Position')
probability=abs(startingpos-position(length(position)))/15*100
%%
count=0
TF=isprime(position);
B=nnz(TF(1,:)==1);
if numel(B)>=4 && numel(B)<=9
    count=count+1;
end
probu=sum(probability);
FinalProb=probu/L;
end
disp(FinalProb)

Answer 1

[Vidhi Agarwal]

Hi @Petch Anuwutthinawin,

I understand you are attempting to work with a piece of code that contains nested loops, and based on the code provided, you are attempting to calculate the average probability over a number of iterations. You want to make sure that these loops operate appropriately across a number of iterations.

To achieve the same you might need to address below given modifications:

• Ensure that the probability calculations are done correctly and accumulated over each iteration.
• Ensure that variables are properly initialized and updated within the loop.
• Compute the average probability after all iterations.

The modified code for the same is given below:

for k = 1:L
    prime = primes(250); % Prime numbers less than 250
    Prob_prime = 0.85;   % Setup for prime probability
    Prob_other = 0.3;

    startingpos = randi(250, 1, 1); % Random starting position between 1 and 250
    position = zeros(1, 15); % Preallocate the position array for efficiency
    position(1) = startingpos; % Set the first position

    for f = 2:15 % Loop for moves after the first position
        r = randi(2, 1, 1);
        if position(f-1) == 1
            position(f) = 2;
        elseif position(f-1) == 250
            position(f) = 249;
        elseif r == 1
            position(f) = position(f-1) + 1;
        else
            position(f) = position(f-1) - 1;
        end

        % Calculate probabilities
        x1 = Prob_prime * position(f-1);
        x2 = Prob_other * position(f-1);
        d1 = position(f-1) - x1;
        d2 = position(f-1) - x2;
    end

    % Calculate probability of ending position
    probability = abs(startingpos - position(end)) / 15 * 100;
    
    % Accumulate the probability
    totalProbability = totalProbability + probability;
end

% Compute the average probability
FinalProb = totalProbability / L;

Hope this helps!