substracting every row from each other

Question

Selma Nur Keskin 2020-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/543587-substracting-every-row-from-each-other

评论： Selma Nur Keskin 2020-6-7

采纳的回答： madhan ravi

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I am trying to substract every other row using 2 loops, what is wrong with this code?

Here is the code,

% these are the coordinates I am using 
coor=[x' y' z'];
%number of  the rows is my atomnumber 
atomnum=size(x,2);
contactmapdistance=zeros;
for i=atomnum : 1
    for j= 1:atomnum
        contactmapdistance(i,3)=coor(i,:) - coor(j,:);
        i=i-1;
    end
    j=j+1;
end

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Selma Nur Keskin 2020-6-6

If anybody could make this work in two loops so that ı understand how it works it would be great

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Answer 1

madhan ravi 2020-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/543587-substracting-every-row-from-each-other#answer_447377

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coor - reshape(coor.',1,size(coor,2),[])

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Selma Nur Keskin 2020-6-6

I guess this is working but i am such a beginner , what does 463x3x463 double means? when I store the results in a matrix the matrix size looks like that. Thank you very much btw!

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Answer 2

Image Analyst 2020-6-6

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https://ww2.mathworks.cn/matlabcentral/answers/543587-substracting-every-row-from-each-other#answer_447395

编辑：Image Analyst 2020-6-6

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Do you mean like this:

% Initialize data
% numRows = 5
x = randi(9, numRows, 1);
y = randi(9, numRows, 1);
z = randi(9, numRows, 1);
% These are the coordinates I am using 
coor = [x(:), y(:), z(:)]
% number of  the rows is my atomnumber 
% atomnum = size(x, 2)
contactMapDistance = zeros(ceil(numRows/2) - 1, 3);
% Subtract row 1 from row 3, row 3 from row 5, row 5 from row 7, etc.
cRow = 1;
for row = 1 : 2 : numRows - 2
    contactMapDistance(cRow, :) = coor(row+2, :) - coor(row, :);
    cRow = cRow + 1;
end
contactMapDistance % Show in command window

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Image Analyst 2020-6-6

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Like this:

coor = [x(:), y(:), z(:)]
contactMapDistance = coor(1, :) - coor

Note that the way I set up coor is better than your way because my way can handle it no matter if x, y, and z are row vectors or column vectors, which is not true if you use the ' like you did.

Selma Nur Keskin 2020-6-7