I assign A = B; but I could not use A and B interchangeably

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Hi everyone,
I'm trying to make a 3D median filter for a 3D CT image, here is my code:
function I_fted = abc(img, mar)
I_fted = img;
% For-loop to loop through each pixel in x,y,z directions and filtration
for y = 1+mar:size(img,1)-mar %loop through the vertical direction
for x = 1+mar:size(img,2)-mar %loop through the horizontal direction
for z = 1+mar:size(img,3)-mar %loop through the slices
grid = img(y-mar:y+mar, x-mar:x+mar,z-mar:z+mar); %create a cubic grid [mar x mar x mar]
I_fted(y,x,z) = median(grid(:)); %calculate the median of the pixels inside cubic grid
end
end
end
end
I did assign I_fted = img. However, when I use the below commands, the result images are different for each case. I don't know why
% Case 1:
grid = img(y-mar:y+mar, x-mar:x+mar,z-mar:z+mar); %this give different result to the below
% Case 2:
grid = I_fted(y-mar:y+mar, x-mar:x+mar,z-mar:z+mar);
  1 个评论
Walter Roberson
Walter Roberson 2019-9-6
At what point do they become different? You are changing I_fted
By the way, have you considered using nlfilter()

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采纳的回答

James Tursa
James Tursa 2019-9-6
You are changing I_fted inside the loop. If you subsequently use it in another calculation within the loop, it would not be surprising that the results are different from what you would get using img, which was not changed within the loop.

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