Why can't it proceed to the next iteration of for 'runs' loop?

Question

mrbond99 2020-7-6

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评论： mrbond99 2020-7-6

nruns = 10; nphoton = 100; m = nphoton;
for runs = 1:nruns
    q(:,runs) = rand(nphoton,1);
    
    while m > 0
        for i = 1:nphoton
            s(i,runs) = 2*pi*q(i,runs);
            m = m - 1;
        end
      
    end
end

Why array of s only save the first iteration of runs == 1? I can't solve this problem, too much loops. Please help..

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Answer 1

Geoff Hayes 2020-7-6

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在 MATLAB Online 中打开

mrbond99 - please look at the condition for the while loop

while m > 0

You will only enter this loop so long as m is positive...but the body of this loop decrements this variable on each iteration of the for loop. Since it is never reset to nphoton, then this code will never be executed again. I think that you want to move the decrement to this variable outside of the for loop.

for runs = 1:nruns
    q(:,runs) = rand(nphoton,1);
    while m > 0
        for i = 1:nphoton
            s(i,runs) = 2*pi*q(i,runs);
        end
        m = m - 1;
    end
end

Or can you remove the m altogether and reduce the code to simply

for runs = 1:nruns
    q(:,runs) = rand(nphoton,1);
    for i = 1:nphoton
        s(i,runs) = 2*pi*q(i,runs);
    end
end

? Is the m necessary?

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mrbond99 2020-7-6

I need to use m as it refer to how many photons have travelled through a step size, s. I think I solved this problem after reading your comment at ' ...never reset to nphoton'. Thank you very much, Geoff Hayes for your comments and solutions. I appreciate it very much.

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