Assigning values to an array using elements of another array after each element goes through a check

Hello,

Let's say that i have an array (e.g zeros(5,5)).

I'd like to use each element my array has, put each element through an if statement check, make some calculations, and assign that new value to another array that has the same dimensions as my initial one.

If anybody has any idea i'd be of great help!

Thanks!:)

Answer 1

[YT]

I think your looking for something like this

start_matrix = rand(5,5); %rand 5x5, values between 0 and 1 (cause whats the point in comparing zeros)
end_matrix = zeros(size(start_matrix)); %same size as starting matrix

for i = 1:size(start_matrix,1)
    for j = 1:size(start_matrix,2)
        if (start_matrix(i,j) > 0.5)
            end_matrix(i,j) = start_matrix(i,j) * 666; %some crazy calculations
        else
            end_matrix(i,j) = start_matrix(i,j); %no crazy calculations if <= 0.5
        end
    end
end

end_matrix

[Nicolas Martoudes]

It worked perfectly!! Thanks a lot! :)

Answer 2

[Matt J]

I'd like to use each element my array has, put each element through an if statement check

Just be aware that that's normally the kind of thing you try to avoid in MATLAB. For instance, YT's example is much more efficiently implemented as follows for large matrices,

condition =  start_matrix>0.5;

end_matrix=start_matrix;

end_matrix(condition)=start_matrix(condition)*666;

[YT]

I agree to what you said, but I think it's useful for beginners to understand how looping through a matrix works.

[Matt J]

Yes, I know. I just want the OP to be aware of important alternatives.