Error in comparing equal matrices

I am trying to display a success message if the code identifies two matrices which are equal, but I see that it works out only for a few elements of the matrices. Can anyone please correct me if wrong? Here is my code below:

Rotation_matrix = rotm2tform([0.9254 0.0180 0.3785; 0.1632 0.8826 -0.4410; -0.3420 0.4698 0.8138])

res = rpy2tr(30*pi/180,20*pi/180,10*pi/180)

if size(Rotation_matrix==res)
    for i=1:size(Rotation_matrix)
        for j=1:size(Rotation_matrix)
            if Rotation_matrix(i,j)==res(i,j)
                disp("success")
            else
                disp("fail")
            end
        end
    end
else
    disp("Sizes are not equal")
end

Answer 1

[Voss]

It looks like you are trying to loop over both dimensions of two matrices and compare the elements one at a time, and first you check that the sizes are the same. This is how you would do that:

if isequal(size(Rotation_matrix),size(res))
    for i=1:size(Rotation_matrix,1)
        for j=1:size(Rotation_matrix,2)
            if Rotation_matrix(i,j)==res(i,j)
                disp("success")
            else
                disp("fail")
            end
        end
    end
else
    disp("Sizes are not equal")
end

But notice that you can stop checking as soon as you know one element is not the same, if all you need is to know whether the matrices are the same:

if isequal(size(Rotation_matrix),size(res))
    found_a_difference = false;
    for i=1:size(Rotation_matrix,1)
        for j=1:size(Rotation_matrix,2)
            if Rotation_matrix(i,j)==res(i,j)
                disp("success")
            else
                disp("fail")
                found_a_difference = true;
                break
            end
        end
        if found_a_difference
            break
        end
    end
else
    disp("Sizes are not equal")
end

Or, a better and simpler solution to the entire problem of comparing two matrices is just to use isequal once (if you don't care about which element(s) are different):

if isequal(Rotation_matrix,res)
    disp('matrices are the same');
else
    disp('matrices are different');
end

[DGM]

Considering that this is all probably done in floats, it might be worth using a tolerance

tol = 1E-12; % or something
if all(abs(Rotation_matrix - res) <= tol)
    disp('matrices are the same');
else
    disp('matrices are different');
end

[N/A]

Hi, thanks a lot for this. I tried the isequal() method several times (because that is the most suggested), but it does not work unfortunately. It still displays "matrices are different". I used the tolerance as 0.0001 and it works. Really appreciate your help.