How to fast process a calculation within a matrix without using a loop?

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Leon 2019-3-29

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https://ww2.mathworks.cn/matlabcentral/answers/453347-how-to-fast-process-a-calculation-within-a-matrix-without-using-a-loop

编辑： Leon 2019-3-29

I have a huge matrix A, and what i need to do is to go through each of the matrix element and do this below simple calculation:

[m n] = size(A);
for i=1:m
    for j=1:n
        B(i,j) = 10^-A(i,j);
    end
end

The thing is that it is slow. Is there a way I can avoid the loop and make it faster?

Thank you!

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Rik 2019-3-29

编辑：Rik 2019-3-29

Whenever the size of an array increases, Matlab has to create a copy in memory. This takes a lot of time if you repeat that very often. Your original code would cause the output to be extended m+n-1 times.

Pre-allocation would solve this issue by creating an array in advance of the correct size. If array processing is not possible, it is generally worth it to pre-allocate the output array.

Leon 2019-3-29