"plus/minus" sign operator

Question

frwmetric 2013-5-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/76146-plus-minus-sign-operator

Hi

I have a row matrix which is like n=[x,y,z] I need to consider plus and minus signs at the same time and get a permutations of them. In conclusion I need that solutions

n=[x,y,z]
n=[-x,y,z]
n=[x,-y,z]
n=[x,y,-z]
n=[-x,-y,z]
n=[-x,y,-z]
n=[x,-y,-z]
n=[-x,-y,-z]

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Answer 1

Iain 2013-5-17

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https://ww2.mathworks.cn/matlabcentral/answers/76146-plus-minus-sign-operator#answer_85785

It depends what you want to do with it.

M = [1 1 1; 1 1 -1; 1 -1 1; 1 -1 -1; -1 1 1; -1 1 -1; -1 -1 1; -1 -1 -1];

Out = (M * Row')' ;

Each row of Out is what you want.

You might want to programatically generate M if you have more columns on your row.

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Iman Ansari 2013-5-17

在 MATLAB Online 中打开

[a b c]=meshgrid([-1 1]);
M=[a(:) b(:) c(:)];

frwmetric 2013-5-17

thank you...

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Answer 2

C.J. Harris 2013-5-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/76146-plus-minus-sign-operator#answer_85792

在 MATLAB Online 中打开

Not exactly elegant, but it works:

A = [1 2 3];
B = (dec2bin(0:2^length(A)-1) - '0');
C = sum(B .* repmat(A, 2^length(A), 1), length(A)) + sum(~B .* repmat(-A, 2^length(A), 1), length(A));