how can i make the centre elements of a matrix to become zeros

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Weisz Thomas
Weisz Thomas 2018-12-9
编辑： Jan 2018-12-11
I am writting a function that takes an n-by-m matrix and and an odd interger k as input arguments. both n and m are odd numbers as well and are all bigger than k. the function should return the input argument with its center k-by-k matrix zeroed out. this is how my function looks like currently and it is not producing the correct output. please help.
function A= cancel_middle(A,k)
for ii=1:k
for jj=1:k
A(end/2+1/2:end/2+1/2)=0;
end
end
end

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采纳的回答

Jan
Jan 2018-12-9
编辑：Jan 2018-12-11
The body of the loop does not use the indices ii and jj at all, so the code does not depend on k in any way.
Call size at first to determine the dimension of A. Then find out, which indices will be affected, if you need k rows and columns at the center. You do not need loops to assign the zeros, but the approach A(c1:c2, r1:r2) = 0 is sufficient.

更多回答（2 个）

Elijah Smith
Elijah Smith 2018-12-9
编辑：Elijah Smith 2018-12-9
this is what I came up with:
function A = cancel_middle(A, k)
[n, m] = size(A);
array2add = zeros(k);
if n > k && m > k
A((floor(n/2) - floor(k/2) + 1):(floor(n/2) - floor(k/2) + k), (floor(m/2) - floor(k/2) + 1):(floor(m/2) - floor(k/2) + k)) = array2add;
end
end
it just replace the middle k-by-k matrix with zeros and if the rows/cols are add it defaults to the top left.
Image Analyst
Image Analyst 2018-12-9
编辑：Image Analyst 2018-12-9
Try getting rid of the for loops and just finding the middle element and setting it to zero
middleLinearIndex = ceil(numel(A) / 2);
A(middleLinearIndex) = 0;

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