MATLAB: Can we vectorize this kind of for loop

dependencyfor loopMATLABspeed upvectorization

The for loop is as follows:
    N=2;T=3;
    Trials=rand(N,T);
    for i=1:N
        for j=1:T
            AverageValue=mean2(Trials);
            Trials(i,j)=Trials(i,j)-AverageValue;
        end
    end
The difficult is that 'AverageValue' changes its value according to each updated 'Trials'.
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Updated version with 'mean2' replaced by 'trapz':
    N=4;T=5;
    Trials=rand(N,T);
    for i=1:N
        for j=1:T
            IntValue=trapz(trapz(Trials(1:3,2:5)));
            Trials(i,j)=Trials(i,j)+IntValue;
        end
    end
Please help, thank you!

Best Answer

I agree with Sean's general point, that for-loops needn't be vectorized at all costs. However, you can make this particular for-loop much more efficient (for large N and T) by incrementally updating AverageValue:
    N=2;T=3;
    Trials=rand(N,T);
   AverageValue=mean2(Trials);
   coeff=1-1/N/T;    
    for i=1:N
        for j=1:T
             Trials(i,j)=Trials(i,j)-AverageValue;
             AverageValue=AverageValue*coeff;
        end
    end
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