Storing values form a while loop within a for loop.

Hi, I've tried to run a while loop a hundred times with a for loop. My goal is to store the counting variable (k) from each while-loop In a vector, and then take the mean of this vector. I've coded it this way;

Q = zeros(1,100); 

for (ii) = 1 : 100  

      k = 0 ; %counting variabel 

      sum = 0;
      critical_value = 1.9;
      while sum<critical_value
          sum = rand(1) + rand(1) ;
          k = k + 1;

      end 
      Q(1,k) = k;
  end

W = mean(Q(1,k));

My problem is that the values I try to store don´t really make sense compared to what I intended it to be. The end goal of this project is to test the mean of the stored counting variables against an predetermined expected value.

Do anyone have a suggestion on how to solve my problem?

Answer 1

[Guillaume]

for (ii) =

That is not a valid matlab syntax

Q(k) = k

Well, that just store the value of k at index k, so Q will end up as Q = [1 2 3 4 5 6 ...]. Note that if k is greater than 100, it will resize your predeclared Q so that it has k elements.

I think you meant to have

Q(ii) = k;  %note that using Q(1, ii) is pointless, since Q is a vector

And of course

W = mean(Q(1,k));

calculates the mean of just one element of Q (whichever k was reached on the 100th iteration of the for loop). You probably meant

W = mean(Q);

Note that using variable names that have meaning would avoid confusion over what ii and k stand for, e.g:

stepbyrepeat = zeros(1, 100);
for repeat = 1:100
   step = 0;
   %... while ...
   stepbyrepeat(repeat) = step;
end

And finally, do not use sum as a variable name. It prevents you from using the sum function.